The notion of "well you will get value from it over time" isn't, imo, a great way to frame it. Even if your feature set doesn't grow, you have connections to external services, and they will have changes over time that you'll need to keep up with (auth protocol changes, etc). That takes attention and time and money. BUT... perhaps a "standalone" version that doesn't connect with asana/google/etc. might have a 'one time price'?
