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After looking at both the Caldera Geneva and the Coleman 471, I'd say he's comparing apples to apples.
The first advice I'd give is to make sure you're comparing apples to apples. When you walk about one spa at $9300 and another at $6200 I imagine you're comparing a large top of the line spa with another spa model that probably is not similarly equiped.
They both went on to add that the reason some manufactures fully foam is to same $ on the manufacturing (foam is cheaper than producing a thicker shell.) Not sure I buy into that