Maybe just release and sell a complete and polished product? And add significant value to that product again before asking for more money? What about the notion of having enough pride and confidence in your work that you can make a solid value proposition regularly, and not yoke your customers to you permanently with a nebulous agreement?
Also, practically, consumers in the audio software market are more savvy and have higher expectations than those in other markets. In particular, they expect a fair ownership model (something provided by many plugin and DAW shops, big or small), and are wary of subscriptions and things like them. Perpetual licenses are the norm - in fact, even things uncommon in other software markets like the ability to resell your licenses are often provided due to market pressure.
Also, practically, consumers in the audio software market are more savvy and have higher expectations than those in other markets. In particular, they expect a fair ownership model (something provided by many plugin and DAW shops, big or small), and are wary of subscriptions and things like them. Perpetual licenses are the norm - in fact, even things uncommon in other software markets like the ability to resell your licenses are often provided due to market pressure.