We bought our coop from Amish builders which are fairly common here in the Northeast.
It was not cheap---$1300 for a 4x6 foot (not counting egg box) structure.
But it is built like a brick ****house. Insulated roof, architectural shingles, Duratemp siding, working windows, hydraulic lift on very heavy egg box lid. Everything is heavy and tight and solid. I went out there after heavy rains and winds and the inside was nice and dry.
Yes, I looked at the Tractor Supply ones. Cute and a lot less expensive, yeah, but....

My husband is capable of building just about anything---we have gutted and redone two homes entirely, from the studs in and out. Bathrooms, kitchens, beautiful sheds, etc, etc, etc.
But health problems have necessitated a dialing down of the big projects so we bit the bullet and bought a coop. He is crazy meticulous about his projects (he went out in the dark and laser-levelled the chicken run structure) and we visited numerous coop dealers before we settled on one. The coop was made to order (we switched the standard pop door and people door positions, chose the structure material, color, roofing shingles, etc). We skipped any extras that we were willing to do ourselves.
I am so sorry that people are being ripped off by these unscrupulous companies. And $600 is not something most of us can toss into the wind!!! Really sad to hear that so many are being deceived!!
This is the company that built our coop:
http://www.thehenhousecollection.com/
Here it is---last week, with the run in progress:
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