Why the boost percentage says nothing
A boost from 2.80 to 4.00 is shown as "+43%". That compares the bookmaker with itself. If its normal price was far below fair, the boosted one can still be below fair. Only the fair odds tell you whether the boost has value.
The fair odds here come from Pinnacle, the bookmaker professional bettors follow, with its margin removed. The same method is behind every Sharp Bets pick and the EV calculator.
Which boosts tend to be worth it
Boosts on the main markets (match result, goals over/under, handicap) can be real value, and they're the ones that can be checked here.
Player boosts and bet builders are harder. Pinnacle rarely prices them, and a bet builder stacks the margin of every leg, so a boost often only brings the price back towards fair. That's why the check says it can't judge them rather than guess.
Small stakes, small value
Most boosts have a maximum stake, often a few hundred kronor. A 10% edge on 200 kr is worth about 20 kr on average, and a single boost is mostly luck. Boosts are a small extra, not a way to make money.
For the bigger picture of how far luck moves results, try the variance simulator.