Kidd isn't overpaid at all, this is a pretty fair deal IMO. In spite of his age/dropoff he's still a top 10 PG who gives:
1. 40% 3-PT shooting
2. premier rebounding PG
3. capable wing defender
4. good passing (duh)
5. durability-missed only 1 game outta 126 as a Maverick
6. Intangibles-people mock that "2nd best player in league" thing by Cuban, but its based off respectable statistics such as on/off and adjusted +/-, both of which Kidd finished in Top 10 last year. So even if his box scores aren't impressive, Kidd still has a significant impact on games. Not insinuating he's a top 10 player, of course, just saying.
We love our Kidd!