I am doing the same thing! I am trying to find or wait until a good promo code/promo comes up. Even without it, I looking at less than $160 for envelopes, RSVPs, and invitations for 100 of each (We're inviting 80 people, but, if we get a lot of no's to invite others, coffee gets spilled on them, or whatever...we want extra to cover our butts! lol)
I am doing the design, so that part we don't have to pay for either
I got mine vistaprint.ca each invite with an rsvp was 90 cents each plus tax. I got it along with my save the date cards because they were having a sale. Right now I believe their sale is 71 cents per rsvp and 62 cents per invitation.
$35 custom package on Etsy which included Thank you, RSVP and Invitations. It cost $80 to have them printed professionally at a local shop. I found envelopes at Michael's for $30 and we had them all printed for $90. We also got matching custom stamps made at Canada Post when they were on sale. I think they were $1.15 each.
We bought blank cards and envelopes at Michaels $7/50. Planning on printing a engagement picture putting it on the front with scrapbook corners, printing the invite as a picture or on paper and putting it on the inside.
I ordered from Vistaprint. My total was $270 and I ordered 150 invites, 150 rsvp cards, 10 magnets and 120 stickers (to seal the envelopes). Cost also depends on the type to paper you want the invites on. They were also super quick on delivery. I did not pay for the quick shipping just the regular shipping yet I ordered on a Friday and received it that Monday. Everyone compliments on on how nice the invites are.