Comment by hermitcrab

Programmers are famously hard to sell software to. Because:

a) They think they could do it themself in a weekend. Even though it took you 5 person years of work.

b) They are used to using lot of free and opensource software and don't expect to pay for software.

Other technical users (chemical engineers, civil engineers etc) are probably easier to sell to. But I don't have any data to back that up.