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.