At 500k Euros it’s way more expensive than the cheaper Portugal GV options used to be, but with Portugal tightening the law it seems more on par.
If Bulgaria actually processes its visas on time, seems it could be way more attractive than Portugal from that respect? If it actually leads to citizenship, which is hard to confirm (some websites claim it does, but it’s clearly a less well trodden path than the Portugal GV).
Bulgaria is not a Shengen, and bulgarian residence does not even allows to travel freely in EU, plus it looks like you need to invest into government bonds or some projects. Its economy is in worse shape than Portugal.
For people with US passports, this is not an issue. In fact, it is possibly a bonus, since staying in Portugal on an “automatically extended” residence permit causes problems if you exit through other Schengen countries, while other Schengen countries don’t care about extra stay in Bulgaria at all.
Even if you don’t have a US passport, “travel freely in EU” you can do with a $100 Schengen tourist visa, no need to get a Golden Visa just for that.
And in the end if you get a Bulgarian passport, that is an EU passport just like Portugal’s for purposes of EU treaty rights to study and work in EU countries, Schengen is irrelevant.
And the really big bonus - Bulgaria’s tax rates are extremely low. Comparable to NHR, but you don’t even have to apply for anything. So if you can get a remote job, there is no major tax downside to actually residing in Bulgaria, compared to Portugal’s steep taxes.