yeah, I worked in the industry at one of the big names for a while.
I just did a search and this was somewhere on the first page of google:
http://www.asiainspection.com/
"1. Create your account and schedule your inspection in minutes
2. Send an inspector anywhere in Asia within 48 hours from $288 USD.
3. Receive your detailed reports online, the same day of the inspection"
However you look at it, charging basically comes down to hours. Variables are where is the factory (i.e. travel time), complexity of the job (i.e. grade and seniority of the Engineer doing the inspection), and how often you need inspections (100%? Or sampling?).
Sorry, can't guide you with the current pricing, you'll need to check around: SGS, UL are two of the biggest names, but there must be lots of newones springing up. Again, if you're exposed to a significant business risk from quality concerns, don't cut corners.
ALTERNATIVELY ... if you DO try to hire your own staff to do inspections, ping me, can maybe reduce the risk for you, but this isn't the place to discuss it!