I try to sign quality coaches up and down in the minors. But that doesn't mean overspending.
Two things to remember:
1) You can promote a coach. For example, there may be 5-10 pitching coaches listed among the Low-A choices who are as good or better than the bulk of the High-A coaches. Offer one of them a contract at the High-A minimum, and there's a decent chance you'll land him without overspending.
2) If you are getting into bidding wars to fill, say, your AAA coaching positions, withdraw your offers and then wait until the end of the coach signing period. There are usually a few quality major-league coaches who go unsigned. Some of them will be willing to go down a level at a significant discount to what they were originally seeking. You may not be able to sign someone for the $240,000 minimum, but you might not have to pay a ton more for quality. And that coach may then be interested in staying with your franchise the following year -- as a major-league coach -- for a reasonable price.