I like to do this when there's an upcoming "extra" I'm needing to charge the parents for, like Ballet exams or costumes etc.
In the newsletter that announces the payment is due, the paragraph before is always about something FREE.
Eg. I'll write about a FREE pizza party we're having in class on last week of term, or a FREE make-up live tutorial for parents, or a FREE guest teacher class for the students.
I'm sure it's transparent to some, but the framing of it does make a difference. And if it's worded cleverly, from a position of excitement rather than boasting of your generosity, then it helps.
I think it just makes that extra cost look a little more bearable, and us studio owners look a little less greedy... even though ironically the exam money doesn't even go to us, it goes straight to the syllabus organisation.
There's another technique that can be used when writing a newsletter, and that is to quickly distract the parent from fixating on the negative (the cost) with some shocking, exciting, special news in the next paragraph.
Also, putting photos of students looking happy in the newsletter subconsciously reminds the parents WHY they do all this anyway, and bear the stress and expense of it all.