It's a formula. And they take a piece.
If you bet on a team that'll was originally -110 they have to be -125ish from what I have seen to get your money back dollar for dollar.
I tend to think it's not positive ev. But for people who hedge with live bets it's an easier way to hedge you just cash out.
I tend to stay away from the option but like everything in life to day is never a good option would be stubborn.
For example I was heavy on a tennis match this morning. She rolled her ankle and tried to play thru. You could tell she was done. Maybe a cash out there would have been smart.
I said a lot to basically say I wouldn't rely on this but you may find spots where the option is good.