If/then function with drop down lists

I'm trying to create an interactive proposal tool for our sales team. The tool should be able to calculate the a cost based on several colums worth of information. On my current spreadsheet Column A is for Quantity, Column B for the equipment type (which is a drop down list - let's call the things widgets 1-5) and column C is where I'd like the fancy stuff to come in.

Can I ask excel to calculate an extended cost using that data? Basically, it breaks down to an if/then function, but I'm not sure excel with cooperate with a drop down list in the mix.

Suppose:

IF Widget 1, THEN Quantity*$3
IF Widget 2, THEN Quantity*$5
IF Widget 3, THEN Quantity*$7
IF any other widget, THEN Quantity*$4

My formula would have worked just fine if it weren't for the drop down box. They didn't teach combining if/then functions when I took my excel class years ago. Perhaps because you can't? If anyone knows how, I'd sure appreciate the tutorial!

ETA: I've attached a copy of the workbook as it exists now. Cell M13 contains the cleanest version of the formula I've tried:

=IF(C13=curtain, A13*70, IF(C13=overhead, C13*23, IF(C13=wireless, C13*85, C13*4)))