That top gun meet is pretty crazy. They have lots of categories. The realism competition is unbelievable. I have a 8.5' wingspan RC plane (prop) I designed myself and it seems small compared to some of those.
I've seen a turbine powered Concorde that was HUGE and a turbine C-17 that was pretty HUGE too. Those are way too much $$$ that can be better spent on real flying though. (full scale) some of those jet guys coulda almost built a LongEZ or something for what they have in the toys.
For the "Top Gun" scale championship level planes it's about craftsmanship more than cost. Some of them are built starting with "kits" you can buy with 'glass fuselages and wings and such stating in the several hundred dollar range, and some are scratch built buy the owners from balsa and ply or 'glass or CF.
Then they spend an ass full of time fabricating all the details themselves.
The engines and radios and some of the other components are available off the shelf or adapted from other industries. Modified Chainsaw motors and the like. For the average plane in that link, I'd guess that including the owner's time spent fabricating, materials, and gear, the cost would be many thousand dollars and up.
The turbines are generally built by smaller manufacturers specializing in that sort of stuff for R/C, and can cost thousands each.
This event showcases the "Top" of the line and generally also the most time & cash intensive planes.
At the other end of the scale (and pretty much just as dorky/fun) you can get a nice looking scale plane pretty much almost ready to fly with the gear you need for anywhere from a few hundred to several thousand, depending if you are interested in gas power, electric power, or jets, and depending on the size and sophistication of the planes.
If someone is looking for something a little less demanding on time & cash, this distributor is a good place to explore: