The Supercard has long been the cheapass GBA flashcard (if not nearly the only for a few years as the world ran out of 3in1's in quantity), and it's probably still available from the usual Chinese ecommerces, but it's cheap for multiple well deserved reasons - you can polish a turd but it still remains a turd
Yes the price of the Omega has climbed a bit compared to when I bought it (2017? about half a year after launch) but it's still under 50 € on Aliexpress, that's barely more than the full official price of 1 original game and frankly cheap flashcards is a historical aberration caused by the... "revolution for DS" and confined to that console (in fact, only for most-but-not-all Slot-1 cards), I remember the time around 2014 you're thinking of (when you could get a cheap 3in1 as long as it was the Lite), but that too was a discontinued product on clearance despite having basically no direct competition