I would imagine the license costs for dev tools for a startup are neglible. If you run Azure you would setup test/staging instances and tear them down when not in use, again because of scale, I would imagine that cost is negligible.
As for usage costs, doesn't Azure use the same model as all the others, e.g. EC2, in that cost = compute hours (i.e. instance running) + data transfer + storage? So if by usage you mean ultra accurate per CPU millisecond billing, then I don't anyone does that? Would be great though. Happy to be proved wrong though, I'm no expert on this...