getting back to your original posting, let me ask you a few questions..
1) what brand of window/door makers is in your area, for instance up here, Marvin Windows/doors is the bigger supplier, as well as Pella, that the contractors buy from and install.
in other parts of the country, Anderson is number 1 supplier.
2) did you try a licensed contractor in your area, as opposed to the window company themselves?
the contractors, since they "push" the vendor for supplies, discounts faster delivery, have more clout than any of us ever would.
also, the contractor may have another company/vendor he buys from, or several other warehouses.
he can get better pricing, that he "might" pass on to you, but don't really expect that either. afterall, he needs to make a profit to stay in business.
i have found that the local people who "contract" with Lowes/Home Depot, are not always the cream of the crop contractors, but this is where YOU will have the final word as all you have to do is call the store to complain, and they will send someone else out for corrections. many times, they are either first starting out and need to build thier own customer base, or they are well known contractors, that need to fill in work for slower times, to keep thier people working, rather than to lay them off.
in the end, it's not a crap shoot, as much as it is a waiting game.
best of luck.