$3.... GMK Red ESC, although I have entered one of the Elite Keyboards Clack draw rounds. I ordered a $5 BSP Red ESC, but they were out of stock, so I got a refund.
Got my most valuable cap (Cinnn Iron man) in a giveaway (thank you Spamray!) and it holds pride of place on my ergo board. The only backlit cap on that board and the only artisan I own (so far). I will not pay above the artists' price for an artisan cap on principal (helps me limit my keyboard spending to new board parts and Group Buy keycap sets)...
I have spent a decent amount in a single keycap set Group buy, though, and way too much in total.