Just curious, you guys make or buy your building flats? I was looking on eBay and thought they were a little high. I experimented and made my own. I just printed off a picture onto card stock paper, then cut it out and glued to some of my scrap foam board.
If all you need is a flat, that's a better option than purchasing them, in my opinion.
Even a low relief building is pretty easy to make, especially if you download some textures from the web. Or you can use commercial texture paper and door and window castings, which is still cheaper than buying a model kit.
I'm not sure if this qualifies as a flat, but I made backgrounds for my tiny 4x8 layout the old-school way: trees, lichen and some building fronts on foam core. Probably cheesy to today's railroader, but it works for me.