I'm not seeing the answer here. If you multiply everything by 10 then the only metric that means anything -- players' time invested -- remains the same. Same amount of time played yields the same relative growth in credits which buys the same chunk of hardware. And the next exploit to emerge would cause the same relative disparity between those with the time and inclination to grind it and those without.
I do agree that the price of spacecraft -- especially the cheap runabouts -- seems ridiculously low, but only in relation to the average galactic price for commodities. In relation to other players' wealth it's largely irrelevant for the reasons stated above.
The more time a player can invest in a game, the more "stuff" they will have compared with other players. That's inevitable, but of little consequence in this game, unless you're talking about Powerplay or high-end competitive PVP where you're expecting to lose from time to time and the war chest can pay for lots of rebuys, repairs and rearming. And even rearming is chump change, unless you're flying a torpedo boat.
One thing that might act as a money sink would be more believable running costs, scaling with the cost of the ship. Fuel and maintenance. It's something the very early versions had but, when players complained, the expenses they were nerfed instead of being balanced and they've never really come back. As soon as you can afford to buy a given ship you can basically afford to run it forever and not even think about the cost. Hell, most people only do a full repair when the paint's too worn.
I'd like to see bits of the ship getting more inefficient and even breaking down completely if not maintained. FE2 modelled this in a largely binary way with the jump drive (marginally increased chance of a misjump followed by catastrophic damage) but the options in ED could be much more interesting. Imagine an FSD that burns more fuel per jump because it's not been tuned or had an AFMU run over it in a while, or gimballed weapons that suddenly jam in one orientation when they overheat.
Whether to pay to repair these from limited funds, or live with the short-term consequences in the hope of a "big score" on the next trade run or mission, should be a serious consideration. But then we're back to the problem of the cheap cost of hardware. The repair cost would have to be less than the replacement cost, otherwise everyone will just swap a worn module for a new one. And because the purchase prices are so low, repair prices would be irrelevant in the same way that fuel costs are irrelevant.
I'm not sure there's an answer to this, but I'd start by reintroducing the percentage loss for selling hardware back to the Outfitters. It makes no sense that we can return worn hardware for the same price that we paid for it, especially now we have the option to store things. Maybe there's a midpoint; pay 1,000,000 for your module and accept a 20% loss if you sell it, or pay 5,000,000 for the same module "plus insurance" that guarantees the same 5,000,000 back if it's returned. An encouragement to buy only what you really need for most players, and a temporary money sink for super-rich experimenters.
On the flip-side, perhaps the Outfitters should offer a premium price for selling Engineered hardware back to them, on the grounds that you've increased its value by the time invested. I wouldn't want to see these modules purchasable by other players, as that would be a shortcut around Engineering. But it would be nice if, say, refitting a former combat ship for trade you could get some reward for having taken time to Engineer the weapons.
Still, most of this is moot. The magic credit spigots are spewing forth their contents into the galaxy as ever they did. Occasional exploits just temporarily increase the magic pressure. Trying to decide where the credit sinks or spending balances should be in ED is like trying to decide which bottle to fill with water while standing under Niagara Falls. Sooner or later they'll all be full whatever you do.