@alexatkin
This is a totaly different approach than a PC running UAE. This price for a totally new hardware isn't exactly excessive. It would cost you more to buy a second hand amiga 500 and (new or used) scan-doubler. Also given the fact an SD card reader is not available for the A500 at any cost..
Could they have made and sold this for less? It doesn't matter. The design is free to use, anyone who feels it is too expensive from A-Cube is free to manufacture their own to sell for less ;-)