So, this is essentially fraud. A contractor has represented the value of his work at $X, when in reality it's only worth $1/2X (or whatever the actual figure is). In this situation, you do have rights, regardless of how much it was your decision to research costs and choose a contractor.

You can indeed take it up with your CC company, particularly if it's a card through your bank. Your bank is more likely to back you in resolving a dispute than an independent credit issuing company like Citibank or something. Idk what Canada's consumer protections are like, but I'm sure they're as or more robust than America's and you can plead fraud as a basis for disputing a charge. Failing resolution from your CC people, you can take it to small claims court (or Canadian equivalent). This would obviously take a lot more of your time and you'd have to also collect evidence that the contractor acted fraudulently towards you, but it's definitely an acceptable grievance to bring to a court.