Most teams do not own their arenas. Most have similar deals as the Wings/Pistons where the city owns it and leases it back to the teams.
But $3B would be the very bottom for the Pistons IMO. Suns sold at a valuation of $4B. Their market is slightly larger but not a billion dollars bigger. Pacers just sold at a $3.4B valuation and their market is quite a bit smaller than Detroit.