I'd ask the geo guy to redo that pay back calc including the well drilling this time.
Your gas rate isn't that high.
I'd also ask why its a 1/2 ton larger then what the Trane guy is putting in, and why only 10 KW of strip. Will that be enough to heat the house if the HP failed when it was at OD design temp.
I'd ask both what their load calcs came out to.