Personally, I've never dealt with COMEX (CRIMEX) nor intend to but I'll chime in anyhow.
When I go to the refiners to 'melt' down gold scrap, they charge me a $30 fee regardless of amount. That said, only certain assayed bars are COMEX worthy and it'd be easier for you to sell your 100-oz bar an purchase and 'approved' COMEX type for storage. There's a list on the NYMEX of which ones they approve of.
But that would defeat the purpose of buying and selling on COMEX - you would have to pay a dealer's markup/markdown...
I am trying to compare the costs of acquiring physical gold through COMEX, and selling it back through there again. I looked on the net, and found the information nowhere. Some assayers do not even take orders from individuals!
So I investigated, and found some details.
Exec summary: (COMEX 100oz gold) appx $9 for the first bar, $3/bar thereafter - with come caveats - see below.
First, one would have to deliver the bar to a COMEX depository (NY area)
Then the assayer would have to go out there, weigh and sample the bar, and take the sample back to lab to assay.
Assay charges are $300 per sample. Travel charges for a professional comex approved assayer to a local comex depository are about 600.
So, for about $900, one can have a bar assayed and put into the COMEX 'good delivery' depository system, or about $9/oz for 1 bar, $3 for each additional bar.
Now, this is not for everyone. You must be willing to put out 120K for a bar, and be willing to go fetch it (might get carjacked on the way home!!), then find a local place to keep it (bank vault?)