I tagged that bidder, not that it matters much since it's obviously a throwaway account.
Even if you were a Legendary earning 0.0375
BTC/week in Chipmixer (which you wouldn't even have to have that rank for), it would take you over 11 weeks to break even--and that's even IF you could get accepted into that campaign or one that pays a similar rate, which isn't likely.
I think $3000 for a Legendary account is a huge waste of money. If you're a shitposter who can't speak English to save your life, you're risking getting banned or blacklisted from campaigns. To most of the desperate spammers, that's an enormous sum of money to be putting at risk.
Perhaps the reason for buying that account is to get merits as some of those accounts come with about 200 sMerit.
The seller doesn't mention any of that, so I suspect there will be no sMerits included in that account. Don't you think the seller would have sold the sMerits or used them to rank up other accounts he's looking to sell?