To everyone who so kindly responded to my inquiry, thank you for your professional expertise. What I've walked away with is that I probably should have walked around with the appraiser (which I didn't) and pointed out the improvements that were done. I have made a valiant effort to bring the omissions to the attention of the appraiser, the company, the realtor, the buyer's lawyer and that's about all I can do. I've made an offer to the buyer to meet her half-way in the middle between the agreed upon selling price and the low appraisal. She agreed. I have to cut my losses, lick my wounds and move on. This finished space served as my music teaching studio for several years, our spot for our at-home tailgate parities and New Year's Eve parities, and my son and daughter's favorite guest room when they come home for a visit. For me, it was well worth the investment that I put into it for the use we got out of it. Realistically, I probably value it for more than it's professionally worth, from what I read.