One guinea pig usually costs between $10 and $40. One normally buys two guinea pigs, as they need social interaction with their kind. Monthly upkeep costs can be in the $70 range.
The first possibility is to get one for free. Your second potential source is adoption from an animal shelter. Your third potential source to purchase from is a breeder. The cost here is likely to be between $25-$50...
It is estimated that there are 13 main guinea pig breeds and several newer varieties in the USA. Their cost varies according to their several characteristics.
While guinea pigs may be fairly cheap to buy, the real cost comes with providing a properly equipped and resourced living space, as well as providing food and medical care...