Uuhh, too many questions, Jon. I'll try a few, though.
I raced 6 days which amounted to 14 races. Cost for the entery fees was about £120 per day on average. Petrol, food, etc, you'll be able to estimate. Bike maintenance is expensive on mine, so we won't mention that part. Crashing cost me two footpegs, a lever, a clutch cover, and a fairing respray. Let's call that £200. Tyres I got at Costco for less than they paid for them. They made a mistake and I got three sets. Maybe I should've put a Costco sticker on the bike for compensation.
. I used two sets of tyres, about £160 a set.
Now, if you are comparing racing and trackdays on your basis, you'll not go racing. The truth is that racing makes absolutely no sense, and you can't justify it rationally.
BUT, if you haven't raced you haven't lived. (Blimey, must stay off the bottle for a while...)