I agree and leave all my sites branded. Most people know that when they visit a niche forum, it’s IPS, Xenforo, vbulletin, phpbb or other. If it would help my traffic or other to remove, I would pay to have it removed. I don’t think it does.
$500 is a bit steep but it’s their hill to put out there. Xenforo is $350 so not much less. Vbulletin is $289. So everyone charges something!
I don’t have an issue and want IPS to have more clients (self-hosted selfishly) so they prosper and continue on..