If you are using professionally-made invitations, visit at least three vendors to compare card costs. It's likely that you'll find the same invitation package at different prices. Invitation manufacturers give dealers a choice of markup fees, making it necessary to shop around.
The biggest factor when determining card cost is the paper the wedding invitations are printed on. A thick paper made out of materials such as silk or cotton will cost much more than lightweight card stock. Different methods of printing also will influence the price; for instance, raised lettering and engraving are more expensive than offset printing.
In terms of historical statistics, in 2003 the average wedding invitation cost per order was for 150 and a total bill of $450 (not including tax and shipping). If you choose to make your own invitations, the card cost will likely go way down.
Searching some of the larger wedding invitation retailers shows some numbers that suggest what you're likely to pay for each invitation. The invitation card cost generally falls between $70 and $500 per 100 invitations. The least expensive invitations are non-fold, single cards with text only; no graphics or decorations. Envelopes run somewhere between $20 and $80 per 100. Lined invitations are the most expensive, but add a lot of class to the invitation. RSVP cards and thank you notes both run between $30 to $70 per 100. Save on RSVP cards by choosing single cards rather than folded ones. This will also save on postage; you'll only need to attach postcard stamps instead of first-class envelope stamps. Or avoid RSVP cards altogether by asking guests to respond via a web site. Details such as cording, ribbon, textured paper, colored ink and vellum all add to the final card cost.
Handmade invitations generally cost less that $1 to $3 each to make. A bride who was recently married made her own invitations for 15 cents apiece and paid less than $100 total. She later went shopping with a friend for wedding invitations and saw a very similar invitation being sold by a retailer for $4 a piece. If you have the time, it really pays to make them yourself and save big on wedding invitation costs.