Petco's reputation for feeders isn't good, but keep in mind that in a large chain like Petco, their suppliers will vary by region, so your experience may be very different from someone else's.
Just to be clear, I don't buy rodents- I raise my own & have for decades, literally. But ones I've seen people post positively about are these, not in any particular order:
https://perfectprey.com/
https://bigcheeserodents.com/
http://www.coldbloodedcafe.com/
https://www.rodentpro.com/categories/frozen-foods/rats
https://www.laynelabs.com/product/frozen-rats/
https://therodentbarn.com/
Buying online WILL be expensive if you're only feeding one or only a few snakes- because while the rodent prices are quite good, you have to factor in the cost of shipping an order fast & on ice- and that's what makes them expensive, unless you buy enough to last a while, like 6 mos. to a year.
Check the locations for the above sources- most allow local pick-up, so if you happen to be close enough, that would be a way around the cost of shipping. IF you're lucky enough to be able to pick them up locally, be sure to transport in an ice chest & on ice. Any delay in your travel could cause melting & spoilage, especially this hot weather.
If you don't need many rodents, try asking around- there may be someone breeding their own nearby that can supply you a few, OR, there may be another snake-keeper you could split an online order with.