The eBay charge is tiny.. maybe a buck or two just to list. Consignment means the place that is doing the selling for you will take a small commission. My question then is "why sell it on consignment when all you need to do it alone is a computer and an internet connection."? If it's a good bike it'll sell no problem. If it's junk you may have a hard time moving it.
I sell tons on eBay, and shipping is a total *****. I've
found that I get the same amount of money (or nearly
as much) just listening on Craigslist, and I don't have
to hassle with packing and shipping.