Burton Lumber- Salt Lake City They can't design a truss Salt Lake City, Utah

Should Burton's Incompetence cost me $3200?

Burton Lumber gave me a bid on a commercial building, but would not sign a contract or lock in their price, they only kept telling me that lumber prices kept going up.  I went to a competitor and got a price in-line with the price that I had originally been quoted by Burton, I informed Burton that they had not been responsive and that I intended to contract with a competitor. 

Burton then informed me that their prices had increased about $6000-$8000 above their original quote, when I informed them that was too much and I would go with a competitor we agreed to split the difference and increase their price $4000.   Then Burton lumber sent over the design for the floor trusses.  

 A floor truss is much like a roof truss in that it is not solid and has cross members.  The advantage of using a floor truss system is so that building systems like:  Heating, plumbing, and electrical can be in the floor trusses and not suspended below them. 

Burton's floor truss design did not allow any openings for the heating system.  When I pointed this out to them they told me it would cost an extra $4000 to re-design the floor trusses.  I think they were trying to make up for the amount they had tried to over bill me before. 

Luckily they had not signed the contract that I asked them to and I felt that even if we worked this out any extra thing was going to cost $4000 to get back their money they wanted.  I informed them that I would not pay this and would go with a competitor. 

Everything to this point, except for a truss design that doesn't allow for heating is just typical negotiations. 

Then Burton informed me that I owed them for the design they had already done just to price the job (mind you that any lumber company had to do this to bid the job). I disagreed with this and told them that instead of billing for their incompetent work they should fire their designer.   Burton lumber has sent me a bill for their incompetence of over $3200.00.