I've definitely been tempted by designer products on several occasions, but the cost of the items is usually enough to deter me. I do have a soft spot for handbags, though - can't seem to get enough of those... >_<
I use to have this issue; to counter it I just stopped going to shop for clothes unless I needed some new ones. Though I'll still buy designer brands since they are usually higher quality and tend to suit my style more. Because of those main two reasons I don't really have a problem with buying designer brands.