OP When I first read your OP I was also getting ripped off, only unlike you they won.
I'm having a building built. Not even halfway through I asked for an upgrade on something yet to be done and the contractor/builder told me it would be $2,500 extra which I quickly agreed to, even though it was a bit steep.
When your OP was first on here my contractor told me he would email the invoice for the extra $. I was expecting it to be $2,500 instead it was $8,500!
I emailed him back (to keep everything in writing) and questioned it and he told me the increased cost was for 'dirt work' in the foundation. This was all supposed to be covered in the original bid which my husband and son agreed to haul in the dirt and they did what they were supposed to. They dumped it the dirt (with dump trucks) into the foundation so a concrete floor could be poured on top.
My husband and son did their part, which took many days of hauling in dirt, many big truck loads, but the contractor, when questioned, started going on about "I don't work for free" which made me suspect some sort of MH issues. I have been told he has screamed and raved at other clients when they questioned anything. I paid up because I wanted the building completed.
I think the way I quickly agreed to the $2,500 upgrade and didn't haggle or complain made him think I was Miss Moneybags, but now with the extra $6,000 he demanded I've over my building budget and won't be able to afford some inside work to be completed.
This contractor has built two other buildings for my husband and son's business, and also two additions, and didn't cheat them - just yelled a lot as he does with everyone. My husband and son agree he has ripped me off as they did all the 'dirt work' as they were supposed to.
I believe he took advantage of me because I'm a woman who he could bully and bullshit. But my husband and son both agreed they would have paid up as well instead of taking him to court and having a not even half finished building.
The greedy man has lost all future business with us and I'm watching him like a hawk now. It's a very small community in the middle of nowhere and I know he's desperate for work. I will not be recommending him and will not let him take and publish photos of the finished building as he likes to do. I am so, so angry at losing that $6,000.