Are you looking for serious answers? Because I would sure as hell prefer World Finals 16 to Worlds Finals 2. I'm going to throw this into perspective. If I'm travelling cross country to pay for a 3-day "Greatest Monster Truck Event on the Planet" event with a full day to prepare the track between racing and freestyle, then I'm going to be pretty disappointed if it's some bus/container stacks sitting on the floor in the same way as it was 16 years ago. With time comes changes, and as long as you aren't AC/DC you understand that (sorry/not sorry). Like think about it, if the tracks didn't evolve at all in the past 16 years, don't you think everyone would be complaining about how this sport is so damn stagnant and whatnot? Interest would fly out the window on mass scales. Don't get me wrong, I don't think that the best tracks in all of history are being thrown in front of us (unless we're talking arena-wise, in which case these are very much the best tracks we've seen). But there's not doubt that shows have the highest potential of entertainment in years because the drivers are experienced on the tracks, and know what to expect, and can learn week-to-week on how to get better.
There's a difference between being able to afford something and a purchase being reasonable. I'm in a small band that would one day like to tour, and I also have money in a savings account, so why not buy myself a $1500 van so I can tour? Because I can use my money for more reasonable things (college textbooks are hella expensive), and can also keep it in case of an emergency. It's the same thing with FELD. Why put money into cars that aren't necessary when they already own dirt, and can put the money into expanding their shows and their brand into more countries, and build more trucks? They'll make way more money from expanding into new markets than they would from bringing back cars. Also if the junkyard could pull everything off the car that they could profit from then you'd be left with the subframe if even that. Places like Pull-A-Part have a list of basically every component of a vehicle online and you can buy all of it. This is more than the engine/drivetrain, this is every suspension component, brake component interior component, body panel, and literally anything else on the vehicle. I mean just as an example, Here's a Malibu that was a crush car in Cincinnati a few years back.
This car has been stripped of quite a bit I'd say, at least the front Fascia, headlights, and rear bumper cover. A lot of parts are dinged likely from the loader putting it into place, but there's still money in this car (well if it hadn't been painted and attacked by the loader.) Just as an example, the rims on this 12 year old economy car could still have brought in about $200, and I'm betting the suspension and axles/suspension arms were still in usable condition at minimum. I bet the interior was fine, or usable before monster jam got ahold of it too.
You also mention that the junkyards get the cars back right after, this is true, but after a Monster Jam show, what's the point? Let's be honest, if you saw a car that was clearly used at a monster truck show, even if it doesn't look that bad, you still probably wont pull a part from it because you know that 10,000 lb vehicles have been driving on/over it, and it's painted an obnoxious color. At least I wouldn't. Most of these cars are probably recycled after the show. Whether they sit in a junk yard for a bit beforehand or not, they're only going to pull in about $300 based on their weight, and the steel market has been anything but steady from what I've seen so that's a risky one. It's surely affordable by a company like FELD, but not reasonable.
Business choices are more than what you can afford, but rather what would be best for the expansion, and overall view of your company as a whole.