Printables - where do you get your ink & cardstock?

[bettsiom]

I'm inspired to get Pinterest-y for my lo's 4th birthday party and printing some stuff out at home - invitations and maybe some decor / games related stuff etc - I am wondering about the value / expense of printing at home and wondered where any budget conscious crafters got their printer ink and card stock?

Or are there any bargain digital printers online that will print and post whatever you send for better quality? The local printers where I am are v pricey.

We have an HP DeskJet 2540 printer and I've not dared stray from the HP cartridges, although I am sure they expire over time rather than through use.