I've made the mistake all too often of buying unknown materials (beads, charms, fabric, even clothes!) online without seeing it in person first. I get drawn in by good photography and great prices. And more than half of the time I'm really disappointed in what I receive!
If I'm buying something that's standardized, like 22 gauge, round, half hard, sterling silver wire, I know exactly what I'm getting and can often find deals online that I can't find locally. But with beads, and such, If I haven't already seen it, I know I might get burned online, so I often pay a little more to buy in person.
It's a bummer too, b/c sometimes I buy supplies on Etsy and the quality just isn't very good, but I feel like I can't complain b/c, you know, we're the Etsy family... sigh. Such are the perils of buying online.