If you "just" created it and shared it immediately, there should be no discrepancy. I create and share one every Friday so I just checked my most recent on FB - it's just what I would have expected. HOWEVER, I "share" by copying the promotion link from my browser window and then pasting that into FB. I have not tried sharing through the FAA FB link. Is that what you are doing? (There still should be NO difference, but there are a number of troublesome anomalies in the LTP set-up).
I'm sure you realize this as it's very clear when you create a LTP, but just in case . . . there is a base price that your mark-up is added to. That final figure is the cost that will be shared if you share the link to the promotion.