I googled for embedded USB host controllers and there are a bunch, one of which actually has linux drivers and costs ~$9 on digikey, the Cypress SL811HS.

It doesn't have it's own CPU, so it would still need some $5-10 CPU that we could control over the serial port to twiddle it's lines and such. Or write the host controller directly into the system, but that's more hacking than I prefer to do with my (quickly becoming) irreplacable empeg.