On the one hand, it's not an easy stunt to reproduce. These are great games at a massive discount in a well-publicized event. Not surprising you can make money at that.
On the other hand, none of these games are very new. Games are usually like movies: a lot of sales in the opening weeks followed by a quick convergence to zero as they fall off the radar. A million dollars is not a lot of money split seven ways and then split again among developers. But I'm sure it's great for games headed for the bargain bin.
Certainly there are a lot of games out there great enough in their day to be worth playing even now that technology has moved on. HOTU is evidence enough of that. A service that sold only hand-picked classics, polished for modern platforms, at cheap prices? Yeah. I'd buy that.