I don't understand what is so difficult about opening PayPal, clicking the "Request money" button, pasting in an email and an amount and submitting. For a $350+ purchase a real invoice shouldn't even be a second thought. I did real invoices for $3 keyboard keys in the Lambda group buy. I think what is happening is DrugER didn't want to invoice people, and boost is "invoicing" to DrugER's PayPal so that the PayPal fees don't have to be charged twice (when boost collects, and then when money is sent to DrugER).