Buying a half point

Buying a half point I was at M and bought some Toledo +21 and the guy taking the bet looked stunned that Toledo was getting so many points and suggested buying a half point to get a great price. I declined out of ignorance. I get that I could have gotten +20.5 at a better price, but how much value is there buying off a number like 21 and what is the standard advantage you could gain (financially) from this purchase.
next to none. focus on the 3 and 7.
In CFB, if you're paying 10 cents the only profitable buys are on/off the 3 and 7. 17 is about breakeven.