Very unprofessional and unethical builder. We sign...

Very unprofessional and unethical builder. We signed the purchase agreement (#167-322-1) with Landon Homes for their Lexington Community in Frisco, TX on 01/02/2021. In contract our price was $685,000 for the stucco elevation. Today, 01/11/2021 I got a call from the sales rep saying that we can't entertain your contract because material cost went up and new price is $745,000. He also mentioned that they didn't execute our contract yet so we are not legally bind to entertain the price we offered. I literally asked him while signing our contract that we won't get the price increase after this as we see that you guys keep increasing price. He told us that you are signing the contract on current pricing and its just that we can't execute it now because we have a limit to sell houses per month but you will get this price. Its very frustrating and saddening for us because we passed on a perfect pre-owned home just because this house will be new and built to our taste.