There are tons of companies out there offering cheap, economical logo design. Some use multiple graphic designers for the same price and offer you a number of concepts but if you want additional concepts and increased revisions you can expect your cost to elevate beyond the original list price.
I found a great place where you can get multiple designers to submit their concepts at an affordable price. There is a webmaster forum called Digital Point that is filled with graphic designers, webmasters, promoters and marketers all with tons of Internet experience. There is a section of the website ( Business >> Buy, Sell or Trade >> Contests ) where people interested in getting design work completed can run a contest and have multiple graphic designers pitch their concepts. These designers are then looking for feedback in hopes that they will win the contest.
In the past I have run a $50 & $100 contest for logo designs and have been very pleased with the results. The $100 contest had 41 submissions and there were 5 that I really liked and one jumping out beyond the rest. I accepted the logo and sent the winning designer the $100. What do you think the cost would be at a logo site to have 41 people submit concepts and offer revisions based on your recommendations. I guarantee you it would be much more than $100.
The quality of the work is excellent and there are some very talented graphic design professionals on there. For proof check out this contest thread for a solar panel company called G-Tech. There were 46 concepts submitted in 24 hours for a $50 contest.
I would recommend that you look around the forum for a bit to see what other people have requested, the length of the contest and what they expected in a completed project before submitting your own.
Good luck and drop me a line at firstname.lastname@example.org if I can be of any assistance!