You could jump up to a Zpacks tri-plex for $699 for $22.5 oz. They specifically say the following:
- A separate groundsheet is NOT required for this shelter. The floor material is reasonably durable, and all Dyneema® Composite Fabric gear can be easily patched in the field with repair tape. If you do prefer to use a groundsheet as a precaution, Flat Groundsheets are available.
This tent is a little rich for me, but by your math, you are probably reducing your price per pound savings and reducing your weight by a lot more going to this tent.
I question if the BA tent necessitates a footprint. I haven’t seen the specs for the floor, but it should be sturdier than the fly – otherwise, it doesn’t make sense. I’ve been using a Polycro (window shrink film) with my tarp-tent Notch and I’m starting to think it’s unnecessary. Even so, it would be a lot lighter than the 8 oz. BA footprint. Tyvek would weigh more and I think protect more than Polycro, but would still be lighter and probably a lot cheaper than the BA version.
I think a lot depends on the BA floor material, and your experience and typical campsite. If you are camping around a lot of pine needles or sharp rocky soil, Tyvek may be warranted. If you are willing to deal with leaks by patching with tape, that would be the lightest and cheapest of all.