The way I understand it, actually 75W will be pulled through the 1x slot! That's because of the16x graphics cards usually draw 75W from the 16x slots. Since the card doesn't "know" it's attached to an 1x slot, it does not bother drawing 75W. When you take a look at the pci express pinlayout for example at wikipedia, you will notice that it's only the pins prior to the key notch, that are dealing with power. The rest is for data.

That's also why powered risers provide extra power to the PINS, not the 6+2 pin power connectors.