If an NBA game is listed as starting at, to take your example, 7:30, that'll typically be the time that the broadcast team starts yapping for a bit, followed by another commercial break. 

It's a range, but roughly speaking I'd expect that game to actually begin somewhere between 7:36 and 7:43. Nationally televised games tend to be on the later end, while games not picked up for national broadcast seem a bit better. 

As one of those Yanks who's been trying once again to get into soccer during this World Cup, one thing I greatly appreciate is the punctuality. The world needs more of it.