[silvestrov]

I would say: Praise is only valuable when honest (rather than scarce).

Praise should not be seen as "money": the problem is not the amount.

Praise should be seen as a feedback tool, i.e. getting to know the truth of how valuable the work is. Feedback without honesty is not usable.

[closewith]

Both are true, as praise is absolutely a currency that can be devalued like any other.

Given with abandon, even honestly, it loses its value to both the disponer and recipient. That's something that many in management roles never appreciate and is one of the reasons that some give it too sparingly. They've found that abundant praise loses its utility and come to the incorrect conclusion that scant praise is best.