It makes runabouts and spare ships easier to buy. It makes any items with fixed prices easier to buy. It keeps money from being a major motivating factor if everyone is rich eventually... And money shouldn't be a big motivator in a Star Trek game.
The worst parts about inflation are buying new gear on a first time character (which is a bad idea in any game, generally) and if you want to buy absurdly expensive items then just sell everything you get at inflated prices and you can buy the stuff on there at inflated prices quite easily.
I don't see the downside to an inflated economy in this game.
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