Those are beautiful, but it would take me about 15 years to break even on cost vs buying eggs. Trying to stay in the 3-5 hundred range
First off, if your goal is cheap eggs you're better off buying them from somebody else. There is no way you're ever going to have a viable backyard chicken setup and beat the economies of scale of large commercial poultry farms.
With 20 layers, my eggs still probably cost at least $10 a dozen, but they also provide me pest-control and a source of natural fertilizer for vegetable gardening. Plus I just like having the little twerps around.
If you've got the tools and the skills, you can build something way better than anyuthing pre-fab from $500 of materials.
The problem is with those units is two-fold: they have to be able to sell it for a profit and they have to be able to ship it to you economically. This runs counter to something that is truly sturdy, or has proper ventilation, etc.
They also tend to way over-estimate the number of stanard-size that will comfortably fit in them. Most of the ones that say they'll house 5 to 6 chickens will be lucky to accomodate 3.
And even the "pre-fabs" have a lot of asembly required, and they tend to fall short with things like adequate roosting bars, anti-digging protection, and all the other little details you need for a good coop and run setup.
You can find some great plans for building your own coops online for little or no cost. I found some plans that I paid a $20 donation for that worked well when I altered them to suit my needs and carpentry skills.
You can also repurpose materials as well. I saw some prety clever re-engineering some people have done with things like old but still sound garden sheds with repurposed cabinets for nesting boxes, etc. The forums here have some great DIY advice and examples as well.
I think I saw someone that used old shipping pallets for the basic structure. If you don't have an HOA to worry about or you can hide it behind a fence, you can sacrifice appearnces for utility and come up with something that suits your needs and doesn't break the bank.