Petco doesn't sell piranha so far as I know. At least, the NY stores don't because they have to have a permit to, and Petco is too cheap to spring for a permit for every store. Your Petco sells piranha? You sure they're piranha and not mismarked pacu?
Yeah, the prices at Petco are really jacked up and sometimes it's not even worth paying for their fish either. $1.79 for -a- neon that I could get six for a dollar at the LFS. Petco's best fish bargains is when they have their 99 cent fish sales, and you have the "buy one get one free, limit 3 fish" coupons that AG puts on the back of their stuff, and your PALS card, then you can get a good bargain on fish like gourmis and rainbows. AG has some great Petco coupons like 50 cents off next AG purchase, or 20% of air-line stuff. Just don't forget your PALS card.
They also occasionally do 10% off stand sales. Still, 10% ain't a whole lot, especially for $200 dollar some odd stand.
~~Colesea