Payment is possible in cash, a choice of dark artifacts, or everlasting unlive should the ritual go aas planned... because if not, the whole point is moot anyway 
We say thanks for your business, and we can assure you that you have chosen the right supplier (as we are the only one really doing this).
Your staff and sacrificial subjects are all strictly professionals, we encourage our staff will be working with us until the end of the natural life. We handle all situations with discretion and the occasional burst of a tommy gun. We have been serving all kinds of cult worshipping all eldritch gods you will ever know.
We prefer cash payment please, and please respect our policy, that if you don't got the full amount, we demand your family as payment.