what it takes
I have read all the comments to date on seat covering. First, if you do not have much sewing experience I would suggest you get them done professionally. I have sold a few and due to the time involved my pay ends up being about $5/ hr. The four rv interior seat providers must get discounts on materials or be much faster than I am in order to make a profit. They all do quality work.
If you or your spouse has the time, likes a challenge, wants to make a personal creative contribution to your aircraft and has sewing experience then I would say go for it. It is great to have someone walk up at a fly in and say "who did your interior" and you be able to say "I did it".
If you are looking for an inexpensive seat cover, check out your local auto upholsterer-they can give you a quote and you can compare it to the rv group. Again the rv group of sewers provide a superb quality and fair price.
If you are looking to save money on the interior and don't have the ability to do the seat cushions yourself, you can do the side panels, carpet etc.There is no sewing involved in most of those. It is time consuming to make patterns for all the side panels, but they are not hard to do.