So are credits like bitcoin? Or is it FIAT money? All FIAT money eventually becomes worth the paper its printed on (nothing).
https://i.pinimg.com/736x/26/2e/85/262e859970a0bfe9174875b89b176e47--ludwig-politics.jpg
I think in ED it's like the opposite. Instead of inflation, the goods are worth about the same as at launch (a tonne of gold is still around 9,000Cr despite loads having been mined), our ships are worth about the same but we get paid more for services (missions, bounties etc).
I believe the general & relative value of goods & services was thoughtfully considered & balanced at launch, with the result that you did A-B trading to earn money, and combat & exploration were more purely for rank progression & the challenge.
While subsequent updates have upset the definition of what a Credit actually is, from the perspective of playing a game generally people seem happier to be able to choose more ways to earn the cash for upgrades. It does make some activities (piracy & some A-B trading) look like poor revenue earners in comparison though.
Personally I find straight A-B trading difficult to concentrate on for long periods, and when long distance missions were introduced in 1.4 (1.3?) I was very happy to have a more engaging way to earn my 6-7mCr/Hr. My utmost respect goes to those that attained Trade Elite purely through A-B trading, it's not something I find easy at all.
So I'm happy that there are more ways to earn money, but at the same time a little less happy that the value of being cash rich is somewhat diminished.