Note that this would probably not be required if https://tabsoutliner.userecho.com/topics/146-ability-to-filter-tabs-not-just-use-built-in-search/ was implemented

There is only a very small community of active users. If I charge them a pair of euros this will have no any effect and will not change anything at all. For who use this tool daily the price actually is not that important, it's not some toy from iOS store that you will buy, use one time, and then forget. You need to invest a lot (in terms of time and attention) to even start using this, the $15 after that is just nothing if the tool really becomes useful, and there are some users who just cannot browse anymore without it and use it daily, I am one of them. I plan to raise the price when there will be more features. And definitely I don't want that the users who see no any value in this tool to shape its future, so the adequate price also helps with prioritizing future developments and understanding what the core users of this tool really needs.

Agree with this statement. I'd say typical users are power users, and power users see the benefit in paying a relatively small price for a piece of software that does exactly what you want it to do. Ammortise even $40 over how many hours you will be using the extension, and you'll see that it's actually quite cheap (yet people still pay $25 for a crappy 2 hour movie.. go figure).

It's getting a bit complicated, but maybe create tiers?

I'd love to see this turn into a business as it would mean we get more frequent and reliable updates!