We thought about hiring a pro, but it was just not reasonable with our budget. I didn't DIY as far as designing and printing them myself, but I did assemble them myself (gluing the invitation to the backer, and the backer to the pocket, etc.) and hand-address them myself too. I actually enjoyed the process.
DIY! Got a Michael's kit on clearance for $12 which included 40 invites, envelopes, rsvp cards and envelopes, and a description card for like wedding details. FSIL is an art major and so she designed the invites to have our 2 dogs and cat on them. It was really precious and meaningful to us.
DIY. We purchased the premade pockets at Michaels and I will be doing everything else myself. I'm going to use a free template to print everything then I'm mounting them on cardstock to dress them up and making envelope liners.
I'm doing my own with a pocket card, belly band, foiled invite, rsvp, and details card. This would normally cost around $7-$9 per invite, but by DIYing them, I got it down to $2.20 per invite. Here is my inspiration. I'll have blue, burgundy, silver foiling, and white cardstock for mine.
I will likely assemble them myself (put the different pieces in the pockets and use a belly band). I will either have the addresses printed on the envelopes or hire a calligrapher. I guess this is considered partial-pro.