For example I found AutoMD useful for getting a rough idea of how much the repair might be around.
But then I also want to know how actually trustworthy their estimate is. At least it'd be better if I can get to know how do they work out the estimate. They say here that:
Repair Cost Estimates
AutoMD's Fair Price estimates are calculated for both shop repair and Do-It-Yourself, and are formulated for specificity using average labor costs for each zip code, hours to complete and AutoMD's proprietary real-time market pricing data on millions of vehicle parts - down to engine size and sub-model.
Still not clear enough. How do they get components price / labor costs per types of work / in a specific region?