It seems i did something wrong...
I also bought my FC at Colonia, at the same event. At that time i wasn't really familiar with CGs and if the goal in the bubble will be reached. Also i had no idea how fast i can travel to Colonia in my 56-ly-DBX. So i decided, as Colonia CG made it quite fast to final and i was never there, to start my voyage and buy it there. In fact it wasn't so hard, so i had a lot of time for sightseeing and exploring between.
After buying FC, installing some services, i also bought an Anaconda, Python and T-9 for hauling and mining. After that i was almost bankrupt (at least felt like), Inara says i had roundabout 6.8 billion in assets, 747 mio in Credits (iirc the liquid was lower). Then i started mining Tritium. There are several hotspots in Colonia, one of the rings, where i also mined, got 14 (!) Tritium-Hotspots (pristine of course!). Took me roundabout 2-3 weeks to get 5.000 tons Tritium into my carrier, but i also mined a lot of other valuable stuff that i could sell.
I did some of the usual stuff in Colonia, some missions, unlocking engineers, then started my way back on the same route where i had marked some systems worth a mapping. Somewhere between Bubble and Sag-A (iirc roundabout 8.000 ly from Sag-A) i left my FC behind and made a tour to the centre and around. While my FC was parked it even earned some credits! I had Universal Cartographics installed and some commanders sold there data out in the void - some 100 mio credits more earned. The whole journey i also did some mining for Tritium and of course collected some other ore, with result that roundabout 1.000 ly from bubble another FC-owner dropped in and left 1 billion Credits.
To cut a long story short - i came back after maybe 3 months with a carrier, a reserve of some thousand tons Tritium and enough credits to compensate the "loss" of credits for the FC. I could have been much faster without exploring, but that also earned me some money too.
And today, almost exactly one year later? I could buy three carriers, just from free credits, not to talk about assets. A lot of that was just possible earning with the fleet carrier. So, if someone didn't managed to gain at least the 1,5 billion to compensate the original price for a FC, it's maybe just not his gameplay to own a FC and it's maybe not worth holding one.
If anything isn't fair
@OP, it is that some commanders get their credits doubled, while others not (wait a second... i just talked to a friendly math genius, he told me 3,5 billion x2 is 7 billions! Crazy this math thing... it's magic... that is 2 billion more, than a FC costs! So you can buy a FC and have 2 billion credits more than before!).
It's not fair that you and me could buy that wonderful piece of gameplay (i really won't miss it anymore
) for 30% discount, while other commanders before and after didn't had that chance.