What matters is knowing which way. Here are four structural distortions worth keeping in mind before you read any leaderboard on this site.
Rookie scale contracts are structurally underpaid. A top-5 pick producing like a $30M player on a $12M cap hold looks like a steal, but it's really the CBA working as designed. Teams get four years of cost control as compensation for the draft's inherent risk, so celebrating those contracts as “finds” is a bit of a category error.
Veteran minimums skew the same way. Ring-chasing vets who sign for the minimum are a selection effect, since only the productive ones stick around long enough to keep getting signed. The leaderboard ends up over-rewarding them.
Supermaxes mostly show up as overpays. This one is also structural. Supermaxes get awarded to players who were elite when they signed, and elite-when-signed is a moving target. When a supermax goes underwater in year three, the more likely explanation is that basketball is hard and four-year projections are harder, not that the signing itself was wrong.
“Market value” often isn't. Bird rights let incumbent teams outbid the open market, so a contract that looks overpriced against a regression may simply reflect what it took to retain a player rather than what he would've gotten as a true free agent.
None of this invalidates the metrics; it's most of the reason they're worth reading carefully in the first place. We publish the formulas, the gates, the weights, and the backtests on purpose, so that you can argue with a transparent model rather than having to trust an opaque one.