I would disagree that its more expensive to make your own
We always make our own, both printed & otherwise, you can buy packs of blanks cheaply -
For printed, buy packs of something like this www.amazon.co.uk/Inkjet-Greeting-Paper-Weight-Envelopes/dp/B000W4DRZE/ref=sr_1_4?s=officeproduct&ie=UTF8&qid=1340535471&sr=1-4HERE - when finished the look professional & they work out at less than 50p each - most office suppliers sell them, but do buy online as that cuts the cost right down - I use UKDVD, who are a bit cheaper still, but they are out of stock ATM
Then use your own photos, or download images suitable for the person its needed for from the net, ie; the one I made last night was for a 50th birthday for a friend of DHs, who is an old punk rocker with a big love for one particular punk band - I downloaded an photo of an old gig ticket - took it into THIS FREE ONLINE PHOTO EDITOR & added text - you can do all sorts of other things with images on there too
I was also given THIS LINK by nickel on another thread recently with is also free & looks better than Lunapic if you are a PC user (we use MAC so its no good for us).
If you don't want to print, but craft your designs, you can buy packs of blanks with envelopes cheaply in all kinds of places, even Argos & the works or any craft or stationary suppliers.
Again LOTS you can do, everything from buying lengths of felt - don't buy squares though, as they are expensive - by the meter is MUCH cheaper - usually about £3-4.99 & you can buy 1/4 meters in various colours - cut simple shapes, triangles for trees or angels for example - add glitter, sequins, whatever - you can often pick up packs of these sorts of bits in 99p stores, or Poundland - no need at all to buy the expensive card trims from craft shops - make your own