If any of you have been here for a couple years you know that I used to raise Bangaii Cardinals myself, so I can attest to the work involved.
Well done raising these to salable age, and I concur that $25 is a fair price. (Even though I used to sell them for $20 each if I remember?)
Potential buyers should do their homework before buying. Although these are fairly easy to keep, if you get more than one you run the risk of having two males, and when they reach maturity one will likely kill the other, or severely harass at the least! AFAIK there is still no simple way to sex them visually, which complicates the decision.