I am looking for a high speed laser printer with low ink costs. It
will be doing 30000 peices monthly. I currently use an HP5500DN. It
works well but the ink costs are to high.I need it to print 20 pages
per min.

Don't just look at the cost per cartridge - the page yield of the
cartridge has to be taken into account.
Also, if you haven't yet tried remanufactured laser toner cartridges,
these can provide substantial savings.

There are a lot of companies that sell toner, but quality is very
important when buying from a toner cartridge remanufacturer.

The best prices for the best quality toner cartridges can be found at
http://www.alchemytoners.com (imho)

Check out this site, http://bluedogink.com, they has some laser
printers with low cost on ink, however i recommend using the original
brand cartridges if you are opting for a color laserjet, with a
monochrome you are save with a compatible or remanufactured, but we
have a color laserjet and the generics just do not print color as
well.

Try these, they might help.

http://bluedogink.com/pages-productinfo/product-9368/hewlett-packard-hp-q2670a-black-toner-cartridge.html
http://bluedogink.com/pages-productinfo/product-9375/hewlett-packard-hp-q3960a-black-toner-cartridge.html
http://bluedogink.com/pages-productinfo/product-8977/hewlett-packard-hp-c9730a-black-toner-cartridge.html
http://bluedogink.com/pages-productinfo/product-7218/hewlett-packard-hp-c8550a-black-toner-cartridge.html