What are the costs, or charges markup that scan to pay takes?

Say I have some product or service, for argument's sake say its selling on the site for R1000 (gross, incl. vat, shipping etc.). Then a customer purchases this. What do the pay on the other end? How much do I receive as payment of that transaction on my end? How is VAT and other costs if any applied? Are there API keys? If there how do I get them? What is the service performance rate in hits or usage per given timeframe?