I have repeatedly been told, by people I respect that there is no ladder. A new writer doesn't have to start down at the bottom of the pay heap and move upward. A story will go as far as it can, regardless of the author's previous credits. It's why $10 and $25 and even penny-a-word markets drive Brian (and Jack Haringa) insane.
I believe them. So while I reject the ladder, I resolved to metaphor a different tool; the ratchet. I resolved not to sell any story for less than I had sold a previous story. And it worked. I've sold stories for increasing amounts of money, and now I've actually sold something for "pro," five cents a word.
This leaves me with a small problem. Weird Tales only pays three cents a word, and I'd like to get in those pages. So, do I give up my dream of appearing in Weird Tales, or do I go against my self-imposed ratchet?
I'm currently dodging this decision by writing a novel. I hope I'll have an answer in four months.