People say "that is a value bet" the way they say "that is a nice car" — as an opinion. But value is arithmetic, and it takes exactly two numbers.
A value bet exists when the first is bigger than the second. That is the whole idea. Everything else is argument about number one.
You think a team wins 48% of the time. The price is 2.20.
implied = 1 / 2.20 = 45.5%edge = 48.0% - 45.5% = 2.5 pointsAt 2.20 you need to win 45.5% to break even. If the true number is 48%, the bet is worth making — but only by 2.5 points, which is well inside the error of any estimate you made by eye.
Two failure modes dominate.
One: the fair probability is a feeling wearing a percentage. If you cannot say where 48% came from, you do not have a number, you have a preference.
Two: the edge is smaller than the margin. A 2% edge against a 5% book margin is not an edge, it is a donation with extra steps.
It gives you number two exactly, and it shows how widely number two varies between books on the same match. It cannot give you number one — no software can. That is your call, and it should be written down and checked, not remembered.