One thing to keep in mind, when people talk about the costs to run a year, is that the way of calculating that can be highly variable, so while one person might say "it costs $3,000 per year to run" and another says "it costs $20,000 per year to run" you can easily be talking about the same class of car.
Some of the different accounting variables are (and for each person, they factor differently):
-- First, what I'd call "Lifestyle":
* Doing your own work (i.e., labor costs are effectively $0.00/hr)
* Doing your own towing (i.e., are you factoring in the cost of a tow vehicle, trailer, upkeep and storage)
* Running local events only or going far afield to run on new and different tracks
* "Roughing it" sleeping in a van at the track or getting a hotel room
* Trackside support (doing it yourself, or having a shop maintain your car)
-- Secondly, what I'd call "competitiveness" or "edge":
* How competitive do you want to be?
* are you happy just competing where your speed falls, or do you care about being "out spent for speed"?
* probably some others in here, but you get the idea.
But what I'm saying is, take any class, and make the decision to have your car maintained by a shop (what's known as "arrive and drive" -- you arrive at the track, drive, and then go home at the end of the event), decide you want to be at the pointy end of the field, and that you won't spare expenses (i.e., be out-spent) and you will find yourself spending a lot more money than someone who is content to drive mid-pack ina safe but not very fast car, and who doesn't care that he spent the race behind someone who drove like crud but could afford a fresh blueprinted engine that had just enough more power that he could keep you behind him -- and racing can be inexpensive.
And again, those two scenarios can and do exist in the same class.
Even in SRF there are lots of people that run engines for 6 or 7 years and use tires for 6 or 7 weekends. There are others that pull engines every 2 years and only race on tires for say 2 qualifiers and 2 races and then they become "test" tires. And of course there are lots of folks in the middle, like me.
So you definitely have to make sure you look at the costs in a given class for the type of racing you as an individual want to do. And you have to decide what your priorities are and what's important to you.
For me, that was:
* Arrive and Drive. (don't have a tow vehicle, tools, and more importantly the extra free time)
--- This also meant that I wanted low labor and repair costs, since I would be paing someone by the hour.
* Large fields (number of entries) in my class
--- So I would always have lots of people to race against, as I got better myself
* Reasonable running costs (cost of engines, tires, gearboxes)
--- to help keep costs down
* I didn't want to be easily outspent on money for speed. (admittedly, it always happens, but I wanted to minimize the effect)
* up front purchase costs had to be reasonable but not bottom dollar cheap (I spent $15,000 on a very nice car that was ready to race)
* I had no existing track day car that I was converting, so there was no existing investment.
But there's no doubt different people have different situations. And I would always say "better to be racing at the back of a XYZ field than sitting on the couch."
You do want to understand the costs though, and you may find that some of the seemingly "cheaper" classes don't actually translate to cheaper when you get the accounting equal.
Steve