Cost vs. Comparison Approach- Appraisals

We completed our new home last week. It is very custom, in a rural area with little to no comps...the most recent comp. is over 14 months old as an example.

The comparison approach value on the final appraisal is $25,000 less than the cost approach. Although not a big deal, it would be nice if the bank could use the higher value- I would actually get a few thousand dollars back (I paid the construction loan down significantly) to go towards overages with my contractor.

Are any of you out there mortgage experts and know if this is ever allowed? I asked my bank, but was hoping to get a little insight tonight. I know on the construction loan they used the comp. approach, but perhaps that's because the project wasn't finished yet?

Thanks!