How much for one invite?
PS: $300 is insane, they sell for half that, good luck though. Power to you if you sell it for that.
They
sold for half that a year ago. Now they don't accept new members and there are no sellers active on the forum.
This is one of the best accounts available, because its expiration date is in July 2019 and it's untouched. Probably the last chance to get in. Just try to find another account like this one.
Btw, I've seen people selling MSDN Admins for $400 last fall. I think $300 is a more appropriate price.