I spent the summer looking for the best of inexpensively sourced classical guitars.  As a result, I ended up with a lot of guitars.  My favorites now sport commercially available string sets.  But I wanted to put new strings on the remainder before I gave them away, so I looked for a cheap way of doing this.  

I found Orphee strings on the internet for about $1 per set shipped.  The bass strings of wrapped silk were perfectly acceptable to me.  The treble strings of monofilament were not capable of tuning.  

Many people utilize fluorocarbon fishing line for ukulele strings, so I reasoned that the material might make useful classical guitar strings.  Full spools of this line is quite expensive, but 25 yard mini spools are sold as leader material.  Cost can be further reduced by purchasing what is available on Amazon Warehouse.  I purchased Seaguar  Blue Label 80 pound (0.810 mm) for the 4th string, Berkley Pro Spec 50 pound (0.74 mm) for 5th String, and Ande 20 pound (0.40 mm) for 6th String.  

The Ande may have a coating which promotes sliding, and I had a hard time of knotting it to the tail piece.  Double looping through the tailpiece hole and using three loop wraps (up from the conventional two) solved the problem.  

The sound is excellent, stretch is minimal, and the cost of about $8 per spool is hard to beat.