New Deck—trex or pressure treated

I am a homeowner 19 months into a major renovation project. My contractor has been dragging his feet on every major aspect of the house. We are now ready to build the deck–1300sq ft (included in the contract). We have opted to go with gray Trex or Timbertech with railing system and planters–My contractor is now stating that the deck will cost approx $16,000 more than the wolmanized version included in our contract. Does this seem reasonable? Or should we just go with the pressure treated and then stain the deck—is the yearly maintenance plus staining a wash? please guide us.