the part that caught me was "games costing no more than $100". I'm thinking Phantasy Star at about $70 was the most expensive game of that time, and that was pretty rare.
For $300, I was thinking of ripping on the PC Engine - battery save, composite video out, use ROM cartridges so you could spruce up the board, at least two controller ports.
For games, could you make a 16bit Guitar Hero game? I don't particularly like guitar hero, but it was a thing. Bongo games. Go for broke, and create a whole line of musical instrument controllers - the Sax controller, the bagpiper controller - how else are your games going to cost $100