This is such a bad excuse, just because something is unpreventable doesn't mean it should be allowed. Murders are always going to happen, should we legalise it cause "There is no way to prevent it"?
You are still buying something that you would have otherwise had to work for. The fact that the characters aren't generated for you doesn't make it any less pay to win. It makes it have less of an impact on the server economy though, so it's not as bad as could be.
You seem to be against the idea of buying items for your character, but not aginst the idea of buying a character with items. What is the core difference?
Also, would you not, for example, be able to sell your current character for stars, then buy another similar character with a better belt for slighly more stars, therefore esentially buying gear?
You are trading out-of-game currency for a leveled and (presumably) geared character. You are buying a more powerful charcter. You are buying power.
While this isn't as bad as making something exclusive to paying players (as Sivo so kindly pointed out an example of), it's still buying an advantage and therefore pay to win.
I'd also like to point out that pay to win doesnt mean "The only way to win is to pay" or "If you pay you are guaranteed to win". Pay to win means that by paying you get an unfair advantage over those that choose not to. This is why mounts, tabards and non-combat pets are not pay to win, while donating for gear, characters or xp boosts are.