If you play a fav on the money line, you buy points. Its all about probability, vs the line.
Use a odds calculator, to convert the line to % and it might not be as bad as it looks.
-120,-140 looks awful but instead of 52.38 needed for -110 you go to -54.55 for -120 and 58.33 for -140. This is why 3 in football costs more. To increase your chance of not losing is another way to look at it. Like for the 7 in nhl, I believe 7 lands 21ish % on a 6.5 total, it wont be cheap to increase your chances of not losing by .5 goals for an under.
so then then it comes down to was it worth it. Like someone else said you could also be really good to be worth it, the further off the line is, it could be a good deal. Just as the points cost more the more you want.
Im guilty of it, but I make damn sure if I do, its already on the best line out there. So.... everyone else has +4.0 on an nba game and one place has +4.5, I would say there's no way its that bad for +5.0 for -120. I don't have data or proof, but just a habit. Plus if its a play you thought was worth making before it went to +4.0 everywhere. That type of thing.