I used to play the original Everquest with some friends. One of them had a very wealthy father - like 'multi-millions' wealthy - and he actually paid someone else to play his character almost constantly during the day while he was at work so that he could level up and stay with & play with us kids (who weren't working the hours he was). Eventually he paid the person to take his character all the way to the level cap - but it just wasn't the same, either for the father or for any of us. He didn't experience the excitement of leveling, didn't learn to really play his character the way the rest of us did, and eventually he and his kids all dropped out of EQ because they just weren't having fun.
To be able to buy the top level ships here in this universe/game would, I think, be a similar situation. You wouldn't have really "earned" those ships, you wouldn't really know how to fly them, how to fight with them, and if/when you popped over into MultiPlayer mode, it would - in my opinion - be cheating. Yes, Slim, I know you say you're only playing Solo, but Solo is the same universe as MultiPlayer, you're just invisible to the rest of the players, and they to you. So how does the game world make sure you don't pop in and go rogue on the rest of us, randomly attacking the rest with your super tweaked out Anaconda or Fer de Lance or whatever. Or if not you (you probably are as honest and non-predatory as you say) then someone else who has the cash and decides that will be a fun way to play. Buy in, kill everyone in sight, and if you lose a fight, heck, just buy another ship and be out there an hour later doing it all over again.
In addition, if you're so wealthy that you can buy whatever you want, then you could actually buy several of the best ships, then sell them at a Shipyard and end up with so many credits you could do anything and everything without 'earning' any of it.
Sounds like a recipe for a broken game to me. Hopefully the devs will agree and keep RL cash out of the mix.