Ten?
I built 6, on two accounts, leaving one a starflier.
600 cr an hour is loosely based on rough suppositions that A: They double the previous price, and B: they resale for half that, which many ships do not resale for.
Ten. I'd love to see your documentation on that. I've had accounts banned because of what, exactly? That I attempted to make 600 mill an an hour? Arms traders have earned as much.
That I exploited a glitch? It isn't, so far as I'm aware, a violation of any rule, and this particular method of buying low and selling high on the expectation of changes has been done before. Simply a matter of scale, then?