I think there is a lot of good advice here. You can always give an asking price, even if you think it might be a tad high and then add "OBO". I know that I am rarely going to give the asking price without a little negotiating.
I don't sell much, but buy plenty on here, and while I don't "low ball", I am after a good deal. If you were to list a lot of cranks, say 10 of them and are asking 60% of retail. The buyer might only be interested in 5 of them and, while that isn't a bad deal, you might still have trouble moving them at your price. Obviously, supply and demand is a factor. As a buyer, I tend to buy items out of a want rather than need. That being the case, I look to spend about 40%.
Just thought i would give some perspective from a buyers standpoint.