You can - extremely rarely - get something valuable through the rank-up drop process. I got a skin worth ~$120 (FN M4A1-S Icarus Fell, one of the most valued patterns too) that way. It is incredibly good luck as the rest of what I've got ranges from $3 (once) to about 10c most of the time.

That seems to form part of Valve's escape plan if they're called on this. They can claim that gamers can get the items through other mechanisms that do not require monetary input. In reality, it's vanishingly rare that it happens.