yes they are, one should research the hundreds of companies out there, but i do know when i called 15 of them in feb and march this year,
a permanent 12X40 footer was 700 to 1200 per month, sometimes it involved more than one billboard depending on the location
movable electronic trailers 8 X 12's, 6X8's and 5X7's were almost the same money.
of course if you have 100 billboards in the largest cities (one going into town from both directions), you cover about 90% of the business population. 100,000 per month for say one year would pay for one 30 second advertisement on abc, nbc, cbs, thats why i love billboards.
boss