I know one women who turned down a promotion because on top of not wanting the additional responsibility a $10,000 pay raise based on the formula of the divorce would have lowered his payment by $8500. And she didn’t feel the extra work was worth $1500.
This sounds a lot like the old "I decided not to make more money because the extra taxes would be too much" tales.
I'm not a lawyer, and maybe FL law is different, but in CA your child support (and/or alimony) is set at the time of the hearing. If you want to change it, you would have to request a new hearing and petition for a change. The cost of doing that can be somewhat prohibitive, especially if you have no way to be aware of the promotion (and change of income) in the first place... and doubly so if your own income has changed in the interim.