Hello M., I make all of my beautiful invitations greeting and thank you's, at Sam's Club, (you may also try Cosco and not all Sam's have a photo department). I use their Fuji or Kodak photo maker, as they each have a selection, and with the best photo of my son, that is appropriate for the occasion, create a beautiful custom announcement & invitation card, for between 35 and 50 cents (two sizes), each, and Sam's provides really nice matching envelopes (ask for a few extra for printing mistakes).
The photo machines have a variety of seasonal and event frames, but if you don't see one you like, you can select a nice "border" that you like. If you need help, of one of the employees can show you how to add the text, change the size, color and font, but it's pretty simple. I always add an additional separate text box on the card with the R.S.V.P. request and phone & e-mail information.
And a little secret for the thank you's--do the same for the thank you's--but with great photos from that past event (hand write an individual note on the back)--and for those special people, use a photo of your child with that guest, from the event, on one of their "thank you" border frames, or again, just a border, with your own text. I always get a call and a "thank you" for my thank you cards from those "special" friends and relatives, and all of the guests (even folks that sent a gift and couldn't make it) get two memorable photos of my child--one as an an announcement and a thank you from the event for the gift).
I print the addresses directly on the envelopes with a nice large font.
My niece has a program, and makes her own from her home computer, but with the materials, I am sure hers costs lots more to make. But she does have a wider selection.
I have to add that it is cheap, looks great, and if you have a little time, it's lots of fun--and your guests probably won't toss them into the trash.