Is $13,333 to build a new deck a fair price?

We hired a contractor for a backyard project, which is a new deck build. We paid a 60% deposit before the job started as per the contract. Today, the contractor asked for an additional $2,000 before project completion, claiming prices have increased since the contract was written in March 2025 and that he has already spent the 60% deposit on materials and needs more to buy the rest. This additional amount would take us to 75% of the contracted quote. We told him we would pay the remaining 40% at completion as stated in the contract. There have been some issues along the way, and we are not too happy with him. There were no unexpected issues or changes to the scope of work that would justify this request based on the contract terms.