Why are gothic clothes so expensive? Economics, that's why. Low demand makes it more expensive to produce & sell (sure, we may be scrambling for the stuff, but the vast majority of the buying public isn't). And many gothic clothing businesses, especially the mail order ones, are just a few people sewing things by themselves. It takes them a lot longer to make the clothing although it's often of better quality than stuff you'll see off the rack -- you do get what you pay for.
Of course, that only applies to typical goth clothes -- the velvet capes, poet shirts overflowing w/ruffles, slinky dresses with huge drapey sleeves, pointy-toed boots, etc. Untypical goth clothes are everywhere and at every price -- from velour miniskirts at Target for less than $10 to ruffled blouses at Macy's for about $30 (tip: men looking for affordable ruffled shirts should defintley look thru the plus size women's stores like Lane Bryant!) to crumbling Edwardian dresses for $70 at a vintage shop. Look everywhere, for goth can be found in the unlikeliest of places!