While at the gate 4 people were called up prior to boarding and in exchange for a $10.00 fee received seats 9A, 9B, 9D and 9E.
*****

I love when people post with such authority about things that they have no clue about.

First of all, Employees, their partners AND their families are entitled to space available BF travel. It is an employee perk. They were not upgraded, they listed for, paid for and received an employee perk.

They list for the flights in advance, and they can list in either cabin for said flight. It is not an upgrade. That said, sometimes it feels like one when you don't know if there is going to be any open seats.

Employees, spouse and family members can travel for free in economy, or they can pay a fee for BF (assuming that there is an open seat). The fee is a lot more than $10, it is between $100 and $200 each way (I am not posting the amount as it is company policy not to make such things public).

The fee is usually payroll deducted, so you would not see it being paid for at the gate, secondly, employees get a certain amount of vacation passes (free for BF / F) and they also help standby list seniority.

The $10 fee you saw being paid is actually the departure tax for CDG. When you travel on a non revenue ticket, you have to pay this fee at the gate assuming you get a seat assignment.

So, despite what you stated, they were not upgraded, and as an elite, you should know the rules for International BF flights.

That said, If you did want to drop a further 3k, you should have done it at check in, not once you're at the gate, at checkin they can sell tickets, and if you put 3k down, I am pretty sure that they'd have taken it, but I can't help but feel that if it was no big deal for you to just drop 3k at the gate, then you would have done it at purchase.