5" flowerhorn varys in quality.. I've seen them for 20.00 and seen them for hundreds. So use your own personal judgement and pay as much as you think is worth it.
6" RTC, maybe worth 20.00?
3" frontosa, again varys on which variant it is. Common burundis you can buy for 15.00 or less and zaire blue will cost you alot more at that size.