What do you think is a reasonable mark down for a used item on Craigslist? For example, a snap and go stroller frame that retails for $100-- what would you expect to pay to purchase it from Craiglist?

I've been very lucky in that I have a lot of *free* hand me downs from my sister, and a lot of the big things I want new for one reason or another, but something basic and short lived like the stroller frame I'd be perfectly happy to buy it cheap and used. Not sure what kind of prices to expect/offer. Is there some basic fraction you usually do (1/2 off, 3/4 off?)

Thanks.