Bulk check URLs for duplicate content?

Hi, I am wanting to check about 1600 URLs for duplicate content. I know you can do it with copyscape but it will cost about $80 for the required credits. Is there a desktop tool I can use with proxies or a web tool I can put my sitemap.xml into?

Cheers

As far as I am aware, you'll have to use something like Copyscape. There might be cheaper alternatives...