I got two handbuilt wheels on Tiagra hubs with 36 Sapim DB spokes on decent Rigida rims.
I paid £133 to a well-known LBS with a renowned wheelbuilding reputation.
I've now worked out the cost of buying individual parts from the said shop:
Rear Hub = £25
Front Hub = £21
Spokes x 72 = £32
Rim x 2 = £40
Nipples 72 x 8p = £5.70
Rim tape x 2 = £3
Total = £127
This means they only charged me £6 for building two wheels. I know they will have paid less for the parts than I would as a consumer, but when you only save £6 for building the wheels yourself, and I will never be as good as someone who builds everyday, why would anyone bother painstakingly building their own wheels.
I must add that the shop's parts are sold at very competitive prices so their mark up isn't that much.