AM is far from dead out here in the grain belt. Farmers are old folk who refuse to change, not to mention change the radio in the barn or tractor just for "better sound" which isn't there on a radio of that size.
Here in MN, AM is biiiig money too, WCCO, KSTP-AM, KFAN, etc. So, to say that AM doesn't bring in any money is silly. I'm willing to bet that WOR-AM bills out quite high...
Then again, the AM i took care of in Albany, MN (KASM-AM), a 2100 watt daytimer only, the home to the country's largest vinyl polka collection, if they're lucky sees about $20/spot, or a AM/FM combo buy for $30 ($15/station).
Fear not, AM is alive and well, people like Rush, Beck, Hannity, etc make a living on it's survival. Terrestrial radio in general is very much becoming a target for extinction though.