dave5710 basically explained it all, except the supply chain as far as going thru brinks etc., so here is what i understand it to look like:
1. supermarket gives u change, which u throw in a jar, or something like that.
2. u then bring coins to bank and dump 'em in their machine, and get bills for them.
3. then the bags of coins are filled in the machine (each bag is different in its capacity, halves, quarters & dimes= $1,000, but nickels= $200, and pennies= $50-$100, tho most machine have more than one of each bag)
4. once they r filled the bank stores 'em in their vault till the next coin servicing day. (brinks or what ever come)
5. brinks then gets the bags, puts 'em thru a machine that rolls 'em, they then box them (the rolls), and send them off to banks that need coins, so when u order coins, thats where they come from.
as for how much they charge banks, i dont know, but i know if i order boxes at my local w.f. they would charge me $7.50 per box, altho i wouldnt pay that if it was the last supply bank i had.
hope this helps.