Older S2 body with XML and early driver designs is on the low end...S2+ ranges by emitter and whether it has the metal switch or not (I don't think he's changed pricing based on driver, that I ever noticed anyway). Plus hosts. With the "newer" S2+ models they also have the nicer gift-quality box and a few goodies, which does add to the cost as originally introduced and which aren't included on the lowest price options. Sometimes you might find the same model selling for less at a retailer than you will on Simon's ali site (he wholesales to lots of vendors and I assume quantity pricing breaks are similar to our Western business systems), but if there's a slight premium buying directly from Simon that also includes his great willingness to customize, provide parts and freebies, and ability to answer tech questions about his products. I don't know if tariffs are at play with flashlights right now, or if so whether vendors may be absorbing costs to keep the price points competitive.
Dunno if it accounts for all the difference, but the flashlights-of-color both a) come with the metal clickyswitch vs the rubber-boot switch, and b) come in the fancy presentation box vs the CWC (cheap white cardboard) box.
The $25 S2+ version is an UV flashlight with an expensive emitter, you can’t compare it to the rest. Others in the high range include the battery. Some LEDs are more expensive than others, an XP-L HI is more expensive than an SST20.
You beat me to it, well said. 
The increased cost covers the overhead of producing those batches of extra colors, and the fact that they may not sell well. I’m sure Simon has TONS of stock of the black, grey, etc. hosts but didn’t have any of the fun colors until they were specifically made. Color matching of anodizing is very easy for black as well, whereas with other parts they must all be done at the same time and more care must be given to ensure that matched color.
Those other lights with all colors costing the same is because they were all produced at the same time and if anything the black versions are simply made a bit more expensive to have price parity with the other models (whereas Simon can give the absolute lowest price for highly stocked items without worrying about being stuck with only funky colors that might not be popular because of that).
Got it today well you certainly can’t whine on the prices and the build quality is fine, i think I may have to get more……I ordered the 12 mode group be stoned if i can get it to program.
Certainly only one S2+ is not enough! 
Certainly agree 
where did you get the deep pocket clip?
Every S2+ I've bought (2 total, Osram Orange and Green) or will ever buy (there will be many more) I've also ordered the 18350 bodies and deep carry clips. Also ordered a plethora of TIRs to try out. Have some OP reflectors on the way. The 18350 version of the S2+ is outstanding. Perfect size.
I'm not big into 18650 lights >100mm in length the SC31 Pro / Wurkkos FC11 is about my length limit, but I also 18350 those. FW1A is probably the longest 18650 that has yet to bother me enough to order the shorter tube. The S2+ is better than any of those though. It just is. It's highly customizable. You can order it with any emitter. Any color. Any optic. Different buttons, drivers, different everything. The UI is refreshing to me but most pre-anduril enthusiasts are probably sick of it.
If you don't have one yet get one, any one of them, and get the 18350 tube, and enjoy.
At what part of the ordering process do you ask for any customization?
I have a stack of 18650 most of them from a dismantled ebike battery pack all Samsung 35E.
You can either PM Simon before you order to verify he will agree to a request. And/or after you have placed the order, there is a spot to add message to vendor and you can put your request in there. For anything a bit out of the ordinary I check with him first. He’s only turned me down on request so far and I understand why.
Are these lighted switches, or GITD switch boots?
Neither lighted nor GITD boots come standard on the S2+. The ones with metal switches are just that, plain metal switches. You can buy a lighted switch and change it out yourself if that’s what you want. Likewise you can buy the green or blue boots that GITD to replace the black boot that comes with the light.
Here’s some links to Simon’s store on AliExpress for these optional items:
Just ordered some SST40’s @ $12.
Those colored boots rock. More than once have they helped me find my light in pitch black conditions. Even the orange one, which isn’t GITD, helps.
Also, a reminder: the lighted switches don’t play nicely with Biscotti drivers. You need a bleeder resistor to bridge the gap.
Thanks max for your reply, see below my comments.
In fact I was wondering which device is installed on NeutralFan's lights.
Thanks for your link to a lighted metal switch. But since my S2+ already has a metal switch, can I buy only the lighted switch? I see such lighted switch are also available with translucent rubber boot but is this switch useable in a metal button version of the S2+?
I already did so for my three ZL headlamps, and found out that there are two GITD switch boots categories:
- The good quality ones, made of solid GITD material, i.e. even at close view you cannot see the tiny GITD particles in the silicon, it looks like the silicon itself is the GITD material, and they glow very bright and very long. The only ones I found were these 12mm flat boots from LHT Flashlight Store, and to a lesser extent (8 out of 10 pieces were OK, the other two belong to category #2 below) these 14mm domed boots from the same store. See the pictures in my review of this item, in the Reviews tab of the product page.
- The poor quality ones, made of "basic" colored silicon (green or blue generally) with scarce visible GITD particles inside. They don't glow bright, and not so long. I received quite a few such products that I had to trash, e.g. these 12mm domed boots from Vagtur Store and various sizes and colors from another store (from which I asked and got a refund). For both these, see the pictures in my product reviews, and a comparison example below, between "good" and "bad" GITD boots, all charged with the same light source and for the same time.
I'm afraid the ones sold by Simon (your link) belong to category #2, see the pictures in the currently second review by A***h in the Review tab: you can see brighter dots in a not-so-bright silicon material.
I have not yet found high quality (category #1) boots in 16mm diameter.
I will receive my S2+ this week. It comes with a metal switch like the other colored body S2+ flashlights from Simon. I ordered a cyan colored one: Simon's aliexpress store S2+
I also ordered one of these: Metal lighted switch What I plan to do is to remove the stock metal switch and throw it in the parts box and replace it with the lighted metal switch.
I also don't see any reason why you couldn't replace the metal switch with the lighted boot: Lighted boot switch
The hole in the tailcap is smaller on the metal switch version. The rubber boot won’t fit through.