Only an hour and 30 minute train ride outside of Rome, Sperlonga gives you all the bang for your buck. The Amalfi Coast is far more visited, but it's also a lot more expensive. I stayed at Hotel Mayor for only 45 euro for one night with a continental breakfast included. When I found out the room had a balcony with a view of the sea, I was completely sold.
A last-minute accommodation booking in the Amalfi Coast would have cost at least triple that amount. When you're a budget traveler who's open to experiencing any new destination, it doesn't matter if that place is outrageously famous or not, you just go.