Free Stuff

I have been trying to get rid of 2 old cellphones for the past 3 weeks. The phones are 3 years old but they are in great shape and these phones would still be considered an upgrade for many people out there. I advertised on Craigslist and Kijiji and started the price at $20 per phone. I got a couple offers and then I reduced the price to $15 after getting 2 offers that were lower than my asking price. I got a couple more bites but they didn’t end up coming to pick them up. So I got maybe 4 or 5 offers in 3 weeks or so. Then yesterday I decided enough is enough, I want to get rid of these phones so I put them up for FREE on Craigslist and Kijiji. Within the last 12 hours I have received 18 emails. I am planning on giving it to the first person who inquired but I’m leaving the ad up until them just in case they don’t show. 2 of the 18 people offered to pay me for the phones. Why did the number of inquiries (per hour) jump so much as soon as I made it free? I think the relationship between the asking price and the number of inquiries is highly non-linear when you get closer to $0. I’m curious how many inquiries I would have gotten had I posted them for $10 each (in hindsight the drop from $20 to $15 was too minuscule to make much difference).