Builder trying to have us cancel the contract

[Gina Qing]

Hi BP community, hope all is well. 

We got under contract for a new build with a developer via a realtor (she also represents the seller / the developer) about one year ago. We were informed by the realtor that the developer wants to have the purchase price raised up to market price, which is a huge gap, or he will not deliver the build. The original closing date was in November 2021, and the addendum had revised twice and now is Aug 2022, but the builder is refusing to sign, and hoping we either pay up to the market price, or cancel the contract. 

Could you please give us advice what we'd do, if we choose to enforce this current contract on the developer? Thank you very much in advance. 

Best Regards,