50k low seems a bit out of the norm. Have you presented the appraisal to the listing agent and have them see if they can find comps that the appraiser may have missed. Similarly there may have been improvements to the home such as rooms added or square footage that are not on the tax roll meaning they were done without permits. Thus the seller may believe the home should be valuated as a larger home but the appraiser didn’t give the full ppsf on the improvements because they were made without permits.
Or the sellers just priced the home way above market rates and are convinced someone will come along and pay more then appraised value.
I would advise you to attempt to get a little price relief, perhaps split the difference with the seller. Alternately you can offer to get a second appraisal and split the cost of that with the seller. There are several options.