In my experience, it's not the cost, it's the performance. There are plenty of F-Class shooters that can and will pay pretty much whatever it takes in order to be competitive. I am one of those. However, dropping a bunch of 9's to unexplained vertical in a match is not a recipe for success, regardless of how good the resistance to wind deflection might be. Once you figure that out, the lure of the monolithics is largely gone. In my hands, the monolithics do not seem to behave exactly like lead-core bullets in terms of precision, although it's difficult to put my finger on exactly what the difference is; it's subtle. You can get a load tuned up, but the loads just never seem quite as precise or quite as stable as the those readily achievable with lead-core bullets.
Let's face it, the real (and possibly only) reason most F-Class shooters would have any interest in a copper monolithic bullet is solely for their eye-popping, almost inconceivably high BCs. The uber-high BCs are perceived as being an advantage. By definition, that also limits the game to only a few players in terms of bullets; if the BC isn't markedly higher than a traditional lead-core bullet of similar weight, shooters are not going to spend their money on it, and many of the copper solids, particularly hunting bullets, fall into this category. So there are realistically only a few monolithic bullet choices that represent a significant [theoretical] advantage.
The hard part about deciding whether to try the monolithics is that the BC advantage for a couple of these bullets isn't just a small increase, it's HUGE. That is the real lure that draws in F-Class shooters like a moth to the flame. However, these bullets have been around for a while. This is likely not a case of many other F-Class shooters not having seen these bullets, or being aware that they exist. Yet you don't really see many (if any) people using them regularly in F-Class matches. Even more importantly, no one is winning big matches while using them. They may work really, really well for hitting large steel targets at crazy long distances nearly past the curve of the earth's crust when fired by out of high-performance cartridges with cases almost the size of a ripe banana. But in F-Class rifles, particularly F-TR (i.e. 0.308 Win), the performance hasn't seemed to live up to the lure of the ridiculously high BCs.
So people have tried them, not gotten the results they want, then gone back to lead-core bullets and not really made much if any effort to disseminate their results to others. For that reason, posts will periodically pop up here and elsewhere with shooters that may have only recently become aware of the ridiculously high BCs that then are asking about the monolithics. My observation [and it seems to also apply to many things in life beyond just competition shooting] is that if something seems to good to be true, it probably is.