Raydio is closer to the truth, though last time I was there, the 693AM transmission was up a cage surrounding mast B. But as he says, A and B do NOT radiate at all. It's the T and cage hanging from them (last replaced only a few years ago.

The site has 3 x Harris DX50 AM transmitters already,
But the cost of getting a new 500kW unit is not Millions at all, but about £650k. And to be honest, there are many available in 'part-used' condition. I could find them one for less than £200k, no problem. Indeed, there is a nice TRAM unit available now for less than £100k.

If the will was there, the site could be kept operational for many years at a fraction of the cost it bleeds away now.

The audience for AM is diminishing as so many stations hav been pulled from the MW and LW band, but the rush to digital has made access for more stations and at much lower prices. And with better audio quality.
But it's got precious little to do with some fictitious "rare glass tubes!"