Again the price.

[Lugum]

You are already in a niche market, while most really appreciate it, even understand making a buck out of it, but for many about 2 euro would be the absolute limit to these kind of games.
The recent price increase really makes this hard for instabuys.
It's probably just slap a rom on an emulator anyway.

[rebelstar5]

Agreed. Especially for a rather poor version of Missile Command that's available for free on World of Spectrum to be run by any Spectrum emulator.