How much is my website worth now? - Please advice

I am not looking to sell the site necessarily but I was just wondering how much it is worth.

The domain is http://www.thewebmasterstool.com/

It has a PR4


Revenue is genreated by perminant links in the footer, banner imressions and link impressions.

Also I am selling on it some php scripts which generated over $100 in a month.

Backlinks

I have 467 valid backlinks according to yahoo: http://siteexplorer.search.yahoo.co...wm=i&bwmf=s&bwmo=d&fr=yfp-t-501&fr2=seo-rd-se

and I have 1246 backlinks according to google

http://www.thewebmasterstool.com/ 806
http://www.thewebmasterstool.com/advertise.php 185
http://www.thewebmasterstool.com/domaintools.php 2
http://www.thewebmasterstool.com/htmltools.php 2
http://www.thewebmasterstool.com/linkanalyser.php 2
http://www.thewebmasterstool.com/misctools.php 2
http://www.thewebmasterstool.com/seotools.php 17
http://www.thewebmasterstool.com/directory/ 38
http://www.thewebmasterstool.com/forum/ 13
http://www.thewebmasterstool.com/phpscripts/ 179

Indexed Pages:

Google: 9,650
MSN Search: 123
Yahoo!: 257
AlltheWeb: 248
AltaVista: 254

How much would you say it's worth?

Thanks