How bad could I be sued if I back out of a purchase contract?

[Waleep Alvi]

So, I am in escrow and all contingencies is expired. I also waived appraisal which came in wayy low and now I have to bring in almost 30k extra. I doubt contesting the appraisal will do much. And the seller is not willing to negotiate lower price, so I am pondering the repercussions on backing out now. Reading my purchase contract, it seems like seller will most likely take the earnest. But they can go sue more if they choose. How likely is this to happen? Have any of you experienced this scenario?