I would reject any proposal that stated pricing was subject to change, that would be signing a contract agreeing to what is effectively a blank check.
Well, not quite. It seems that you certainly are legally entitled to be compensated for cost increases.
I posed this question over on the electrical contractor forum to see what they do in this situation. We are no different. There are actually state laws that govern this so check with your attorney. Here is the response from a member there:
Here's my escalation clause, which I think might have come from either NECA or ABC originally:
Notwithstanding any provision herein to the contrary, in the event that, during the performance of this agreement, the price of copper wire and cables, aluminum wire and cables, steel conduit and/or any other necessary commodities significantly increases, through no fault of (your company name), the price of any materials, components, or goods to be furnished under this agreement shall be equitably adjusted by an amount reasonably necessary to cover any such significant price increases. As used herein, a significant price increase shall mean any increase in price exceeding three percent (3%) experienced by (your company name) from the date of the execution of this agreement. Such price increases shall be documented through commercial quotes, invoices, receipts or other such documentation. Where the delivery of materials, components, or goods required under this agreement is delayed, through no fault of (your company name), as a result of the shortage or unavailability of commodities, raw materials, components and/or products, (your company name) shall not be liable for any additional costs or damages associated with such delay(s).
-Hal