I didn't appraise it, but I am in Washington State. Your comments leave so many questions. First, where do you live where you can buy a buildable lot for $3200?
The best method for valuing land is the Sales Comparison Approach. Finding land sales is the best method. Compare them on a price/SF, price/Acre, or price per lot. When that isn't possible extracting the land value out of an improved property is possible.
What were the exact comps used? How much did they sell for and what was the correlated value for your property.
Using a 3200 SF land comp for a 60,000 SF subject is not ideal at all, but I have certainly compared 6000 SF lots to 43560 SF lots, you just have to be confident in your size adjustment. I recently did it and adjusted a property from $80,000 to $96000 for that difference in size.
If the comps were really bad you could call another appraiser and pay them $100 to feed you local land sale comps. It may give you an idea if this appraiser really missed sales. If there are no recent sales go back further in time, go out geographically, or do extraction.
I don't know how to determine if the lots are buildable, but it is a small agricultural community where there is little demand.
Comp #1 65k adjusted to 53k. Comp #2 60k adjusted to 54k. Comp #3 82k adjusted to 79k. Comp #2 is the only one with a comparable size lot.