asymens - check out
www.summerbreezetan.com and click their link that shows you the build out pictures. They ripped up their carpet and stained the concrete. It's a bit of a process, but I think if you or someone close to you is 'handy' you could probably do it.
There are a few web sites that provide good instruction on floor prep. Google "acid stained concrete" and you should be able to find some sites that provide instruction.
Once you tear off the carpet, you'll have to strip all of the glue off and then buff the concrete to 'open up the pores'. You should be able to rent the machines to do it. Once the concrete has been prepped and ready to accept the stain, you apply the acid stain (which you can see if there are any concrete flooring specialists in your area - they will have colors to choose) with a regular garden pump sprayer, wash off the residue with baking powder and water, and then seal it with a concrete sealer.
Go the route of doing it yourself or having some friends/family help you. It will be SO much cheaper. We are using 2 colors, we have 1848 sq feet, so we got 5 gallons of the base coat, 2 gallons of accent color, and 5 gallons of sealer. Total price was $672. I can't wait to do it - I think it's going to look great!