My brilliant and frugal spouse-to-be heard about this outfit at a computer class. Wilton sells blank invitation forms for events that you load into your computer printer and print up yourself. The blank sheets are decorated as usual ones are, with gilded edges, faux bows, and many other attractive motifs. You choose your own font and wording, create a template, and hit "print" to generate as many professional looking and personal invitations as you please.
The invitation stock is available many places, but we found ours on eBay. It only cost about $40 for 120 invitation blanks, including shipping. That's 30 cents per invitation. Try matching that at a print shop!