Blaine County - Appraisal and Info

Can anyone provide information or point us in the right direction regarding Section 16, Township 16 North, Range 13 West (SW/4)? We last leased for $1650/acre at 1/5 but there was no exploration/drilling in the 3-year period and now the lease has expired with no renewal interest (Continental). We now have a purchase offer of $1800/acre. Also, can anyone tell us how much do appraisals generally cost? Thanks. Greg and Sharon.