Hm, very strange. For orders paid by PayPal, we only process the order after we receive IPN from PayPal confirming they'd completed the buyer's payment. This IPN contains all of the data we'd ever receive from PayPal for that purchase, so there is no delay or subsequent update in the data we'd make available to Zapier, which should all be immediately available in full the instant we receive that IPN.
Not sure if this may be relevant, but seems like PayPal IPN has two different types of variable reporting their transaction fees -- mc_fee is their total transaction fee for the buyer's full payment, whereas mc_fee_x is the transaction fee for each specific item's price (where x is a number representing the item's position in the buyer's cart -- e.g., mc_fee_1 for the first item, etc.
If you've been looking at payment_fee and/or payment_fee_x, those appear to be deprecated USD-specific variables that might not work at all in some cases, such as if the buyer isn't paying in USD -- e.g., if they paid in some other currency converted to your USD price.
BTW, thanks for reporting that 404 link. I've updated that now; it just links to a page explaining the same IPN approach you're already using to have PayPal notify us of purchases that didn't originate with E-junkie purchase buttons/links.
