Speaking about rates can get a bit tricky as we need to watch out for "price fixing".  It really is up to an organization as an employer or as the holder of a contract agreement to set their pricing.  So its an open ended question that really comes down to "make sure you read the contract" and potentially review them for more then one if you have multiple to choose from.  Things to consider:

Time: on site, measuring, modelling, paperwork, time with homeowner calls/concerns

Liability

Travel time / equipment/ car maintenance

EA licensing up keep and the cost of education to have it in the first place.

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