Applying for HELOC and appraisal question

[Facundo Gauna]

Hello there, 

I recently applied for a HELOC. The appraisal came back to my home. This is my first time getting a HELOC.

The AMV value is 499K @ 2,350 sq ft with 4/3. There are similar homes in my neighborhood with very similar models of homes and square footage. 

Two weeks ago a house sold for 580K with 5 beds, 3 baths @ 2,350 sq ft with the same floorplan but instead of a loft, there's a bedroom. It showed up as a comparable in the appraisal report.

I guess I was surprised that there's an 80K discrepancy over 1 bedroom. I was expecting it to be more like 540k.

What am I not seeing here? Maybe I needed to see a bigger sample size?
Also, any material on running better comps would be super appreciated.

Thanks!