That's a very good question indeed - and one that's not easy to answer. :-D
Of course, price is important. But it also depends on what you get for the price, i.e. quality, features etc.. The WK30 has with its triple independent emitters - at least for now - a unique selling proposition, so competition is not much of a problem yet. With Sofirn as reputable OEM manufacturer in place, you have a good and reliable partner that BLF members trust.
So, let's do some thinking...
UV light
Switching from LG's LEUVA33U70UL00 395nm to LG's LEUVA33W70RL00 365nm seems to be a highly desired and anticipated change for many flashoholics. Additional costs should be more or less neglectible. Be careful with Nichia's 276A as it seems to be more expensive with less overall output (even though it emits less visible stray light). Maybe you can check with Sofirn how reasonable it is to apply a ZWB2 filter in front of the UV LED to filter out visible stray light.
Red light
There are many lights with orange-red (620-635nm) out there but real™ red (650nm - 670nm) is to be found very rarely. With regard to eyes' adaptation to darkness and to maintain night vision capability as well as to hunt some animals that do not response to these wavelenghts, deep red is more effective. The correct product bin code is XPEBPR-L1-0000-00D01. For instance, the LED is sold by Cutter Australia (https://www.cutter.com.au/product/xpebpr-l1-0000-00d01/). Mouser only charges € 1,50/LED with an MOQ of 100 pcs (https://www.mouser.de/ProductDetail/Cree-Inc/XPEBPR-L1-0000-00D01). So, maybe the deep red version is not more expensive compared to the standard red version.
On a side note: While being more effective in terms of night vision capability one needs to consider that the human eye is less responsive to 660nm compared to 630nm. So, the actual perception might be a bit less bright with deep red.
Knurling
With some slight changes on CNC machining it should be feasible to add some knurling on the tailcap. In return customers will get a better tactile handling when turning the tailcap to use mechanical lockout or to change the battery.
USB port
Using USB-C with QuickCharge 2.0 and moving the port into the thread section of the WK30 will actually drive costs to a higher level. It is questionable if these extra costs will be reasonable with regard to higher sales. However, this might be a nice option or basis for future designs. Sofirn has already integrated an advanced charging circuit into the SP36S (QuickCharge 2.0 capable). Maybe they can reveal some information on how much costs have increased in comparison to the SP36 without QuickCharge 2.0.
Personally and general speaking, everything up to $ 50 is what I deem "budget area". I think a markup of let's say $ 5 - 7 might be still acceptable for some more advanced improvements.