Daniel, dude, I myself have also been keepin my eyeballs peeled for one or more volumes of this series for an affordable price, but thus far to no avail. THE best deal I've seen on any of these was the 2nd volume that popped up a while back on an
online used bookstore-can't remember which one-and that was at $90...............I've never found a better price, haha.
Man though I would love to have all four of the volumes of this series dedicated to the wild plants of Texas. This is quite an interesting subject, and even more so because of the rate at which people are flooding into Texas from other areas, buying up real estate, and so much of our
land being rapidly "developed" (if you want to call an ever-increasing expanse of
concrete, "speculative" housing, and slews of carwashes "improvements", haha) because there is less and less time left to take notice of some of these plants.
Keep an eye out dude, and maybe one or both of us will eventually land good deals on these books. Shoot though, they are such a niche interest, and so low overall book count, that what ones are out there are mostly owned and kept by folks, because those folks wanted them specifically because of possessing an interest in this subject.