How to Determine PRICES for construction work!?!

[Roger Doe]

How do you tell if a price on a job is too high or not?  When you start out, you bid the work out and get several estimates.  But after a while, you have to stop doing that because the contractors will stop coming around because they feel that you are wasting their time.  So, soon, for example, you settle on an electrician that you think you can trust.  But you can never be sure, right?

How do you tell if the next job that they do for you, they aren't taking advantage of you, especially if you have larger buildings?  I definitely notice that the job price goes up by the size of the building.

For example, I just noticed that on one invoice, they didn't put the model number but it was a unique part.  I checked online and the part was only $15 but he charged me $400 just for the replacement.  This was a company I thought I could trust.

So, how do you see if they are charging you a fair price?  Do you ask for the equipment invoices?

Btw, do you guys really ask for certificate of insurance from every vendor and contractor that you use and have them add you as an additionally insured?  Or does that never really gets done.