According to their website, it's going to cost me and my spouse over $40 for a single 7 minute kart race, is that correct? Do people think that's reasonable? Also the membership option (which costs 10 per person) only saves you 2 dollars off karts?

That price is correct. They do run specials on groupon where you can get a better deal.

Don't know about prices I just was visiting the place not a residence

A single adult race would total that much, yes. Maybe you would consider a junior race ,but keep in mind that those karts are a bit tight for adults, but me being 5'10, 190 lbs and size 36 pants I was able to fit but anyone with bigger hips might not. My wife and I did that only because we have 3 kids.