Glossary
Buying points
Buying points means paying a worse price in exchange for shifting a point spread or total in your favor. You accept a lower payout to move the number past a safer spot, trading potential profit for a better chance of winning the bet. It rarely helps unless it crosses a key number.
Sometimes a book lets you nudge a number in your direction for a fee. Instead of taking Granite City at -110 on a point spread of -3, you might pay more, say -130, to bring the spread down to -2.5. You have bought half a point, and the cost shows up as a worse price.
The logic is a trade. You are giving up expected payout in return for a higher chance of the bet landing. Whether that trade is worthwhile depends almost entirely on which numbers you are moving between.
Not all points are worth the same
Buying a half point from -8 to -7.5 does little, because games rarely settle on 8. Buying from -3.5 to -3, or getting off a 3 or a 7, moves you across a key number where a large share of games actually finish. Those are the only buys that tend to justify the premium, and books price them higher precisely because they know the value.
Do the arithmetic first
Buying points is only sound when the improved win chance outweighs the worse price. Off a key number the cost usually exceeds the benefit. Away from one, you are often paying extra for a point that almost never decides your bet.
The same idea applies to totals, where buying a point can pull an over or under across a commonly landed score.