I don't think there is sturdy enough evidence to flag. For all we know, they're a in home rescue (explains quite a few pigs, not giving away the cages), they took in pregnant guinea pigs and are trying to rehome the babies, or had accidental pregnancies. The only thing that is making me maybe think breeder is 'Christmas gifts', but if they weren't expecting babies (for example, bought two pregnant guinea pigs unknown), I can see them trying to get rid of them fast and cheap. I don't think a breeder would sell their 'stock' for just $10. I had a litter of pups (adopted mom from a rescue, unknowingly pregnant) and a litter is very expensive. Definitely more expensive than $10 a pop, at least in my experience.