domain Balloonsbypost.com - what's it worth?

[BalloonsByPost]

Hello,

We are looking to sell the following domains as one group and I was hoping someone might tell me what they might be worth?

balloonsbypost.com
balloonsbypost.co.uk
balloons-by-post.com
balloonsbypost.org.uk
balloonsbypost.org
balloonsbypost.biz
balloonsbypost.info
balloonsbypost.me.uk
balloons-by-post.org.uk
balloons-by-post.org
balloons-by-post.biz
balloons-by-post.info
balloons-by-post.me.uk


The main site has been going about 10 years, has a good reputation and a good natural search position as well as some external links.

Many thanks!