How much would you expect to pay for a PC health check??

Basically anti spyware, antivirus scans, defrag and general performace boosting stuff, done by a professional.

Geek Squad from Best Buy does it for $39.99 I think

Hiya.
In UK at Pc World prices are advertised as : Home check £60, instore, £40.
About 118 US $ and 78 of the same. Dav.

Define "professional."

Is this a "house call" service, or would the customer have to bring their machine to you?

My local charges $78AU in store.