Plumber asking for a lot more money, after starting work
Most of the time the Gas company will provide a larger meter in my area. He quoted the install and missed this. I would verify his license and bonding sounds like ?. Since you won't be running everything at the same time you may not need that big of meter. Call the gas company and ask them for the size required and the cost of an upgraded meter. Then check with the better business bureau and file a complaint if the larger is not needed and the work quoted is not done at the contract price.

Below is part of an Oregon CCB bonding statement -


  The surety bond guarantees that contractors comply with the Oregon Revised Statutes. In the event that the contractor’s non-compliance results in third party damages, a claim may be filed against the bond. A property owner is entitled to file a CCB complaint against a contractor for improper work or breach of contract. The CCB may then direct the contractor to reimburse the property owner for damages for a valid complaint. If the contractor does not do so, the bonding company is obligated to pay the funds due to the property owner, up to the amount of the bond. The contractor is legally obligated to indemnify the surety for any losses as defined in the indemnity section of the surety bond application.


At least in Oregon and Washington states the bond protects the owner from unsafe building. This is true even if it passed inspection and a damage causing failure is later found. I don't remember how many years they can go back, but I keep my old code books, and there used to be an exception for exterior outlets over 6.5'. A buddy of mine put several eve outlets in standard receptacles. A new home owner was putting up Christmas lights in the rain, got shocked and fell. The insurance company and lawyers were going after him for damages because that was no longer the code. I found the code book showing it was legal when it was installed, and he did not have to pay, but it still cost him several thousand dollars in legal costs.