Did it? I remember registering lots of accounts just when it launched because I had a column in tweetdeck with a search that was something like "app.net/invite-code/" (all invite codes URLs started with the same pattern) so every time someone posted an invite URL I got a notification and I could register a new account ;^}
>>akjain+(OP)
It was $50 per account when it first opened, you must have got in when they stopped charging (it was already dying out by this point) but used an invite system.