What To Do With Outdated Equipment? Replacements? Charity? Resell Them?

What does everyone else do with their outdated cameras? We typically lease our cameras to the clients for a period of 5 years as VSAAS. While we've found some use for the older cameras as replacements and some charity deals, we'd like to find a way to offload an ever growing inventory. Although they are mostly Axis P series cameras (a few M's), their value might not be worth the effort of selling them, so I'm looking for all options please. We've considered, recycling them, putting 10 in a box and ensuring that at least 5 of them work and ebay'ing them, and even more charity donations. But, we wouldn't mind reselling them to make a little extra $. All in, we've got about 300 cameras to unload. All ideas welcomed, please and thanks.