Weight savings with a Foamie build vs plywood?

Quick question - I’ve been searching and I’m finding it nearly impossible to locate a “frugal” (read cheap) source of xps foam. However, I’m finding cheap sources of plywood and various sizes of lumber all over Facebook Marketplace.
How much weight is saved with a Foamie camper build vs a plywood/wood small camper build? I hope to build a 6”x10’ vargo type “standy” camper similar to the image below. My tow vehicle weight limit is 1500lbs.
How much weight is saved with a Foamie camper build vs a plywood/wood small camper build? I hope to build a 6”x10’ vargo type “standy” camper similar to the image below. My tow vehicle weight limit is 1500lbs.