... and on the first track day the brakes will overheat, warp, and need replacement. The eco-tires will chunk, the steel wheels will be at much larger risk of bending, and you will have a host of other problems that will arise in the first 3 - 5 track days that are specific weaknesses of the particular model (every car has them to varying degrees, even the super-thrash-happy E30s and Miatas). You wouldn't even get me to drive a stock Civic on a track for fear of lack of prep, let alone take my own Civic out there. Even the Si is not ready for the track. I drove a Scion TC as a pace car a few weeks ago for a Lotus race, and even after the pace lap I had little confidence in the brakes.
I coach track day drivers for a living. I've seen all of the "I want to get on track for X amount of dollars" schemes go up in flames, and I have experienced many of those situations myself. Even a stock BMW M3 is not capable for handling a fast or abusive driver right out of the box at some tracks with lots of grip, like Laguna. *Everything* breaks, and track days make them break a hell of a lot faster. As a result, you don't run anything on a track that you can't afford to replace tomorrow. If you don't, you're asking for it, especially if it's your daily.
If you want to pony up the few hundred bucks per event that it will cost to insure your car, go ahead. That only covers crash damage, so your maintenance costs are still going to be high. Still, if you lose brakes and kill your pride and joy, at least you could get a replacement, and hopefully you didn't spend the value of the car on your premium by that point.
Autocross/autotesting is pretty cheap (here in Scotland at least). I've seen plenty of people drive their own cars to the tracks, thrash about for a few runs and drive home. Or you could go the other route and get a cheap trailer and tow vehicle (if your daily driver won't serve as one). Either of these options would be affordable for most people. Depending on your initial cost (which will depend on which route you go down) and how many events you attend a year, your cost-per-event can be very low (potentially <£100 per event (total cost) amortised over a few years). You're also more in control of your own destiny this way (less chance of being run into by someone else who doesn't care).
Do they require you to work the course at autocross over there? The clubs here make the game cheap by charging small entry fees, allowing 3-4 runs (5 mins track time), then have you work for 1.5 hours catching cones for other cars. I got fed up with it years ago and stopped doing autocross.
After having purchased everything I need, motorbike racing is about $600 USD per weekend for me, assuming I don't crash. That includes entry fees, fuel for the bike, fuel for the tow vehicle, and amortized consumables (mainly tires, which last a few weekends and cost $400 USD for a pair).