Safari have been messing extension developers around for ages now. It's been hugely frustrating. When you dig into the data, most of Safari traffic is from iOS so most devs just can't be bothered to port to Safari. The $99 is just another kick in the face. You might think it's quick and easy to convert, but Safari has all sort of annoying inconsistencies that make it a huge amount of work. For any small software company it's just not worth the effort. Safari should incentivize people not disincentivize them.