Most minimum down payment transactions, such as FHA loans and 5% down conventional loans, require that if the seller contribution exceeds the buyers closing costs and pre-paid items, the excess be returned to the seller. The buyer must meet the minimum cash investment for the loan program. Most lenders do not allow reimbursement of an appraisal fee paid by credit card by the buyer with seller concessions at closing. If the amount of the seller concession is close to the full amount of the buyers closing costs and pre-paids items, ask the lender to wait to charge the buyers credit card and instead collect the appraisal fee at closing. This will increase the chances that the full seller concession in the contract goes to the benefit of the buyer at closing.
As an experienced buyers agent, I speak with the lender before we make the offer. See what it will take to get the closing costs covered and ask for that amount. Asking for the max amount, if the buyer cant use it all, is a waste.