I will say that in my experience buyers have a completely warped sense of the cost of improvements. I can't tell you how many times I've been with a buyer that sees a dated kitchen and says to his/her spouse, "well there's 80 grand to fix up that kitchen". WHAT?! I've heard the same when it comes to landscape....they don't know what they're talking about.

Put the yard in on the cheap. Some sod, a few nice rocks and sprinkler system. Buyer may not love it, but it won't be something that DQ's the house for them. They may be thinking "we don't have $100k for a backyard".