It is about convenience for the advertising. No having to fly the player in to NY or LA to shoot a commercial. No hotel room.
A little more money to the player for being there probably saves time and money for those companies.
I don't think Adidas wants Howard in LA or NYC to save money on hotel rooms and airline tickets for commercial shoots a few times a year. They want him there because those are the two biggest local markets for NBA teams.
That's more eyeballs every game that is shown in the local market. About 3-5 times the households watch a Knicks game in their local market than a Magic game in their local market. The NYC local market has 7.5 million households. The Orlando market has 1.4m. LA has 5.6m. Boston 2.5m.
Then add in the national television exposure the LA and NY teams get, and it's a no brainer to have stars in the big markets.
The top 10 biggest local NBA TV markets - NY, LA, CHI, Philadelphia, Dallas/Fort Worth, SF/Oakland/SJ, BOS, ATL, DC, and Houston. Seven of these ten cities' teams top Forbes' list of most valuable franchises.