I managed a daytime only AM in Houston for years. We leased the station mostly to broadcasters that broadcast to an ethic group in the metro. We had been Spanish, Vietnamese, China Radio and Urban over the years. As for revenue, I could get close to $40,000 a month around 2008. After a power increase (3 kw to 25 kw) and an owner that did not pursue a translator, I was getting push back at $20,000 a month. I could have leased the station for around $18,000 a month with a solid client but my owners felt the signal was worth more. I imagine a mere 2 years later, based on what I've seen, I suspect $15,000 might be tough to get. The FM translator has all the perceived value. An AM daytimer is handicapped by being off the air sunset to sunrise. In a major metro in the winter months, sunrise happens generally after you're in the car on the way to work and goes off the air before you get home from work. (if you left downtown at 5, it would easily be 7 by the time you reached the outer suburbs)That alone is why a daytimer is not desired. If you have some post sunset power you have a chance (keep in mind it is more perception than actuality in the minds of clients). If you have something at night that covers 10% of your market or you have a translator covering 10-25% of you metro there is value but coming on at 7:30am or going off at 5:30 just doesn't work for the client. At least with 10% you have more than 0%.
As for an AM station value, in larger markets that value is almost nil. In some rural areas it is still viable if you do things right, especially if you have a translator or at least night power. It is true night listening is very minimal. Of people I know with a daytimer with no translator, billing $2,000 to about $3,500 a month is not at all rare. Given so many stations are relatively low power or directional, it is pretty much a given an AM daytimer will lose money every month. Directional always is a money pit. If the land and taxes don't get you, the cost of keeping the directional within parameters will, if not this year, certainly in future years.