Karting IMO is the most affordable form of motorsport there is. That said, like all things in racing, your budget is what you chose to make it and there are guys spending big dollars to go kart racing.
I think a big factor in how affordable the sport is to you is how close you live to a track and what programs they run. My karts are garaged at my local track, and the track runs events basically once a month (if not more). So a race day is essentially a set of tires ($200), entry fees ($60-$100), and fuel & food.
Garaging the kart at your track is a big plus IMO. Hauling the karts, while easy enough, increased my trackday expenses by over $100+. Also the loading and unloading added time on both the front and back ends. Now I drive a fuel efficient car to the track for $30.00 in gas, fire the karts up and go karting. Just FYI.
A set of tires is $200.00. You’ll want a new set for a race weekend to be ultra-competitive and managing tires is part of the sport. But then those used sets are good for track days and practice. And there are some guys who run sets for more than one race weekend and still have fun. And some club events mandate tire set usage over time to lower costs. Again, check with your local track and see what they offer.
I think maintenance costs are relatively inline with car costs considering the size of the kart (meaning its a lower operating cost than your 944). But there are times when you’ll find yourself with sticker shock over some spare prices. I guess that’s true for all motorsports.
OK, all that said, karting is a very pure motorsport experience. 75% of everything involving tuning and maintenance you can do yourself. That makes it a very hands-on and personally rewarding experience. And of course when on the track, the handling and power-to-weight ratio is unreal. The speed and agility of the kart is a real rush. The tire slip angles are wide and pushing the limit is forgiving – although smooth is fast, of course. But for someone like yourself, looking to push your focus, concentration, and be competitive, karting is very accessible.
You say you’re spending 10K annually for race your 944. I spend half that as far as operational costs. And that includes $2500 for the garage space. That puts me at the track (not racing) about twice a month minimum – some months up to five times. Race, say half a dozen times a year, and you’ll add $2000 to that figure – give or take. So depending on how close your track is, how much you head to the track – and whether you haul or garage your kart – your annual operational costs might be anywhere from $3000-$7000 for a budgeted karting effort.