It’s not just the towers (antenna array). The transmitter goes too.
To put up another transmitter isn’t a huge deal. To replace that array of towers... that’s a huge deal. AM radio stations don’t do squat without at least a large (200’+) tower for an antenna.
Yep. Multi-tower directional arrays, acres of copper grounding wire. None of it comes cheap. A station up in Johnstown, PA just went dark because they had a 9 or 10 tower directional array. One of the towers crapped out and the owners could not justify the cost of replacing it.
And if you lose the site, you may never find another one where you can stay on the same frequency, serve more then a sliver of your traditional area, and have a pattern with fewer than six nulls.
My hometown station outside Chicago got lucky, I guess. A daytimer that went on the air in 1949, my boss (the PD and CE) told me in 1961 that it would cost them about a hundred thousand (in 1961 dollars!) to go nighttime.
Years later, they did it. Took 4 towers, and a site far from their original one. They probably paid for the new plant with proceeds from the sale of the old site, which had become valuable commercial property by 1980 or so.