樓主不是要擔心怎樣支付這$4000, 而是你的Merchant Account ( 信用卡服務公司) 會直接deduct $40

信用卡 as payment processing cycle:

1 customer place order
2 樓主 charge the credit card
3 merchant service company approve the charge $4000, credit card went through
4 樓主出貨
5 merchant service deposit $4000 into 樓主"s bank account
6 customer receive the goods
7 customer receive the credit card statement
8 customer pay the credit card bill. 到這時樓主才是真正收到了這$4000.