If you stop projects just because no one buys them right of the start, you won't get far. Planning to make a living with them won't get you any further as well.
You created engines for a affordable hobbiest language, so don't await that people pay once again the same as for the language just for a 3D engine, that won't happen.
The chance that you sell more engines will raise if you're price is lower or equal current PC game prices.
But the moment you go above it, you will need to proof that your engine is worth more than buying a new game and that it isn't a "1 shot project" (ie created and sold but never updated or expanded anymore).
An engine, that isn't extended or updated is ok, thats not the problem. But no one would pay more than 20-30$ for it.
You created engines for a affordable hobbiest language, so don't await that people pay once again the same as for the language just for a 3D engine, that won't happen.
The chance that you sell more engines will raise if you're price is lower or equal current PC game prices.
But the moment you go above it, you will need to proof that your engine is worth more than buying a new game and that it isn't a "1 shot project" (ie created and sold but never updated or expanded anymore).
An engine, that isn't extended or updated is ok, thats not the problem. But no one would pay more than 20-30$ for it.