While invitations aren't often considered one of the big ticket items where weddings are concerned, they can be budget breakers. Part of the reason for this is that there are so many choices where invites are concerned. Those choices can quickly take a chunk out of your pocketbook. If the main color of your invitations is white, ivory or a similiar color, matching envelope liners are unnescessary.
Black print is always elegant, and always cheaper than colored ink.
You really don't need 25 more invitations than you think you need. Five to ten additional invitations is usually sufficient. Inner envelopes are unnecessary. They only add more expense. Blotting paper makes no sense in this day and age.