The main “scam” in Peru is simply overcharging. Make sure you have a good idea of what goods and services are worth before you hand your money over. Always agree on a price before accepting a service, such as a taxi ride, or you’ll leave yourself open to service providers charging an arbitrarily high price.
Many of the souvenirs are priced higher and labeled as “handmade” or “artisan”, despite much of them being cheaply mass-produced merchandise. Be wary of overpaying for your trinkets.