The most common way of 'gaming' the system is by drafting a guy in the first round that is willing to take a bonus less than the slot value for the pick, saving money under the total allowable. And then turning around and offering that savings to high schoolers drafted later that were expected to need higher bonuses than their slot values in order to forego college.
Not really an ideal example but it works...
In 2022, the Rangers drafted Kumar Rocker at #3 overall, for which the bonus slot value was $7.59M. Realistically, Rocker had been expected to go much later. MLB Pipeline had him as the 39th best prospect at the time, and he was actually out of school so didn't have a ton of leverage. If we say he would have otherwise gone 10th.. the slot value there is $4.98M. The Rangers actually signed Rocker for $5.2M, saving themselves $2.39M, and Rocker ensured he would get 'good' money, rather than risk falling much later in the draft.
Then in the fourth round they selected Brock Porter, who had been considered (by MLB Pipeline) the #11 overall prospect in the draft. He hadn't already been signed because he had 'firmly' committed to college. Well, the Rangers were able to offer him $3.7M (slot value of $560.2K) because they had saved so much on Rocker, and that $3.7M was enough to convince Porter to sign.
Much shorter example... in 2020 the Orioles drafted Heston Kjerstad at #2 overall (which was higher than he was expected to go), signed him for a little under slot, and then drafted and signed high schooler Coby Mayo in the 4th round. Mayo is one of their top prospects now.
Fun random tactic: Every year there are HSers who are so firmly committed to going to the college - and they make this known - that no team drafts them up top where their talent is warranted. (If a team doesn't sign a drafted player in the top 10 rounds, they actually lose that slot value from their overall pool of money, which they don't want to risk.) But so then teams will usually select those kids in the last few rounds, just in case the team ends up with extra money available, and/or the kid has a change of heart about college. The Nats just drafted (yesterday) the guy MLB Pipeline considers the 107th best prospect in the draft, in the 19th round (James Ellwanger, a high school pitcher). If for whatever reason say their 2nd rounder doesn't sign, they will have $2.14M unexpectedly available to spend elsewhere.