If people buy an expensive ship, expect expensive running costs, and keep plenty of credits aside just in case.
If you have lots of time and go around trading palladium etc by the hundreds of tons hour after hour, the cost of just using a ship matters relatively little. But if you don't, if you have earned it slowly, over time, in small steps, and then, when you finally get the prize of months of effort - you find out that you can't even use the prize because you'd have to keep up the effort that went into just acquiring the thing in the first place. That may be more realistic, but for lots of people it is not fun at all.
And in the end, the higher the average credits/hour a ship eats in fuel, repairs, maintenance etc., the more and more people are entirely excluded from that ship. It should not be necessary at all to min-max your credits/hour rate just to use whatever ship and equipment you have earned yourself. A casual player who has to save up for 2 years until they can afford an Anaconda should totally and viably be able to use the ship, and not find themselves with a useless pile of metal because they must be able to spend a million credits for every hour they fly the ship.
And the fact that bigger ships open up avenues for bigger profits doesn't hold up. Not every profession scales equally. If you are just a pure trader, sure, the bigger your ship, the more tons you can carry, the more money you make. Combat? Exploration? Smuggling? Not so much. And even if they did scale in the same way, that'd still leave us with the problem that you'd be required to follow this one small bit of the profession that is the most profitable of all, just to use your ship.
Upkeep should never be a total drain on your earnings, and the decision to travel around shouldn't revolve around the question "can I afford the fuel, wear&tear?", but "do I want to make a 200Ly journey now to participate the Community Goal". When you come back from a difficult fight, a hard mission - your ship is battered and broken, but in the end you prevailed - it should be a relief, a moment of joy and success when you return to a starport to cash in that mission. Not a moment of horror whether you break even at all.
Apart from the pure "is it fun" aspect, there are also lots of ugly gameplay ramifications from high w&t and hull/module repair cost:
- Long supercruise distances, discouraged. It is already more appealing to fly shorter distances because it takes less time. If it also costs significant chunks of your money, no one will want to deliver a mission to a station 50,000Ls away from the star, when the cost is 3x the payment.
- Fighting on the bare metal, shields down, discouraged. I distinctly remember the time where the mantra was "if you lose your shield, you lost the fight even if you prevailed".
- Silent Running as a combat tactic, discouraged.
- SCBs, and the stacking and spamming thereof, nigh mandatory.
- Long shield recharge times, more than just an big annoyance when fighting with low shields and the risk of damage to your ship is financially devastating.
- Armour upgrades and armour tanking, useless even in PvE. (In PvP they will remain useless no matter what as long as power plant sniping is a thing, or at least automatically easier and quicker than attacking the hull.)
- Any ship that is made to be able to armour tank in exchange for weaker shields, disproportionally disadvantaged. There is a reason why the Dropship is considered almost useless by many, and flown only by few enthusiasts of the ship. But even enthusiasm doesn't pay repairs that exceed mission or bounty payments.
- Experimentation, fun off-the-side activities, novel ship loadouts, discouraged. To pay the bills, you'd need to keep up a certain credits/hour ratio, and anything that falls below that ratio, becomes unviable.
- Interdictions, discouraged. Now we have assassination mission which finally have us seek the target in SC, chase it and interdict it, and the repair/w&t cost incurred become prohibitive again.
And above all else: it should absolutely never cost more to repair your ship (hull+modules just as well as w&t), than self-destructing and claiming insurance. Under no circumstances. Even an A-rated Anaconda worn down to 0% and at 1% health of the hull and every single module, should still be significantly cheaper to repair than to just faceplant into a rock.
