the $500 a year is also needed to use vault, the cloud based parts library. No idea what happens to designs using vault parts if you go off subscription.
Personally I think if we are adopting a beta quality tool, we should be able to buy it on subscription only (no perpetual seat). If Altium really believe in their product, then they will make their $3k over the next 6 years, and probably get AD sales should we upgrade. If the bugs don't get fixed, we are only out $500. There is no way right now I can gamble $3k on it getting fixed
On constructive criticism, it would cost Altium nothing to offer a trade in deal, where you can swap your CS seat for $3k off the purchase of AD. That would make CS much more of a stepping stone then it is at the moment, drive AD sales, and reduce the difficulty of buying CS for your current needs vs AD for your future needs.