We've done them early, once they're covered as long as you don't have delivery trucks or dumpsters driving over them they're fine. That's assuming you put them at appropriate depth, backfill appropriately, manage runoff during construction, etc.
As far as cost 10k didn't really seem that out of wack to me depending on the specs. 2-3 days of guys plus equipment, plus a shitton of gravel adds up. The PVC and landscaping fabric are cheap, but that's about it. In my head I'm assuming you have a normalish quarter acre lot, which means doing 3 sides of the house, one at at least 50', call the 2 long sides 75' towards the street, for a total run of 200'. Even if your cross section is just 2 sq ft for gravel (which is a bit small, do it right and do it once) that's 44 yards of gravel. It's not a small undertaking, but sadly basics like giving water somewhere to go that isn't your house is often ignored.
If you like the house, buy it. In the grand scheme of things 10k is worth a lot less than a good place for your kids, short commute...etc.