Red wigglers are a valuable commodity. I literally started out with 1 lb. of them in my spare room and multiplied them into roughly 25 lbs. Note: This was done in a subdivision with 100 homes, not on a rural farm or large residential 1/2 acre lot.
In terms of money, that's like turning $20 into $500 in a couple of years. If you scale that up a few notches, it's like turning $100 into $2,500. I also sold them in 1/2 lb. amounts for $17, so I really earned more than $500, but it's a nice round figure for demonstration purposes.
I am still vermicomposting today, but after my relocation to Michigan I am doing it on a micro scale compared to the only slightly larger "small" scale that I used to earn the $500 in Florida. I am no longer selling worms to earn money, but after some hardcore brainstorming this weekend I think I need to re-start this project soon. I sold them on Craigslist and quickly received referrals from a local retailer.
Based on my seat-of-the-pants experience and rule-of-thumb calculations 500 lbs of red wigglers would generate more than $10,000 in cash not including sales of the 100's of lbs of vermicast that would be generated. Of course there would be some minimal expenses that would reduce net profitability slightly, but nearly 100% of the inputs for this type of operation can be obtained at zero.