You lot do part with money quickly, don't cha?
$20 is nothing for a feature like this. I understand that, for someone who is using the free version of Stencyl, it's $20 more than they paid for Stencyl, which seem like a lot! However, for a subscriber who is using Stencyl for creating commercial games, a one-off payment of $20 is nothing.
Also, it's a simple matter of economics... If I don't have the extension, then I can't use it to make money. The quicker I have the extension, the quicker I can use it to make money. If I want the feature, I can either develop it myself which is too expensive in terms of time and opportunity cost, or I can sit around and hope that someone else develops it. Alternatively, I can pay $20 (or even $100) and have the feature developed for me whilst, at the same time having some control over the specification.
Also, an extension won't work like this...
To clarify, I'm talking about an extension for 3.0.