you get both kinds though at a booth... its the ones who have the appreciation who wish they could buy everything you have ones that make it worth it.
because, for me I started selling these because, they were piling up ( the ones I could not bring my self to donate. ) I give away a lot of cards too. and I mention that. I have some vista print cards ( free cards ) that I give away it has my blog and gmail (junkmail) addy on them... and people can see that on the blog where I send cards to.
I also think if you do a booth and it goes half way well for you the first year, pay attention to what people ask for. ( if they want daisy cards or anniversary cards try to do a few more of those next time and try to always keep your booth in the same spot)