The S21A is sold for a fair price at Simon's store in AliExpress. It's not that cheap, but you can get a small discount (15%) if you request it by messaging Simon after the order is placed. You must tell him your BLF username when requesting the discount.
For this to work you need to use the AliExpress app or the mobile site because you need to select other payment methods when proceeding to pay (there's a glitch with the desktop site and that option isn't shown). So first add whatever you want to buy from his store to the cart (don't hit buy it now!), then proceed to order and select other payment methods as payment method. When you are presented with the payment page draw back and don't pay, this submits the order. After this go to the order list, click/tap on Contact Seller and message Simon, he will then adjust the order price and after this you can pay.
P.S.: the S21A 2300 lumens? No way. It uses a driver which delivers close to 6 A, and puts out a little bit above 1600 - 1750 lumens on high. Check Terry Oregon's Convoy S21A (Short Technical Review).