It's not really like a garment project. With garments I can look at a pattern piece, understand its weird shape and tell you quite confidently where it should fit in.
With bagmaking, I've found, it's always about a series of interconnected and intelinked rectangles in a range of different materials. Some of the materials are near-identical. But with our house plan, I just see nonsense rectangles floating around on the screen - and I hope they'll fit in correctly. It's a lot like my experience of bagmaking.
What I do know is that labour and expertise are king. You can research and control materials and their costs, but the secret is in the people doing the work. I have probably mangled a lot of good fabrics, and ruined a lot of good projects in my time because I wasn't the right person working with it at that time. The same garment, in the same fabric will look completely different depending on the expertise of the person making it. The same is true in the renovation.
The other thing I know is that the main material is only a portion of the material expense. We have all learned through sewing that splurging on the fabric doesn't obviate the need to spend the money on thread, interfacing, patterns, closures, embellishments etc. Just because I've picked the carpet, doesn't mean I'm not spending any money on the underlay.
Can you tell I'm losing my mind a bit?