I too hate payin that much for a slug. I'm gonna try something else this year. Bit of reloading and casting but if it works it'll drop the price a whole lot.
Lee makes a slug mold. Buy a box of regular birdshot loads, Dump out the shot, cast shot into the slug, insert back into wad and crimp.
Lee is saying their slug mold is for rifled barrels. has a band that will engage the rifling. Here's a link to it at midwayusa.
http://www.midwayusa.com/eproductpage.exe/showproduct?saleitemid=792313&t=11082005
Also look at the Buckhammer slugs, they shoot good in my gun and are a bit less than the rest of the sabot slugs.