I'm a little confused. You want the same yarn as in the book but you don't want to buy expensive yarn? I think most yarns in pattern books are usually higher-priced, natural yarns.

If you want a close match, then you could try looking up the recommended yarn in Yarndex and then search that site for a similar, less expensive yarn with the same qualities. It will also say if the yarn is still being made or if it's discontinued. Or go to sites with a variety of less pricey yarns, like Elann.com or KnitPicks.com, for a close match. Of course these two yarn shops are internet only. I think the internet is where you'll find the real bargains. Sometimes yarn sites have a snail mail ordering option if you don't want to use a credit card. Of course, touching the yarn isn't possible.

Sadly, Yarndex doesn't list the mostly acrylic brands like Lion Brand, Red Heart, or Caron.

Actually, yarndex.com does list Lion Brand and Red Heart, though I didn't find Caron's. It's a great site with lots of info.
Most patterns will list the specifics on the yarn used, such as weight. Choosing a less expensive yarn with the same weight should be fine.

http://gaugebeforebeauty.blogspot.com/

Yarndex does list them? My search was faulty then. Or maybe I only searched on Caron and extrapolated from there.