bulk-buying buffoon
Humorous term for the total jackass that you feel like after making a large-quantity purchase of something in an attempt to save money in the long run, but then discover that you don't need nearly so much of the product as you'd expected you would.
A good example of a bulk-buying buffoon would be someone who liked repairing old VHS cassettes and therefore bought several large rolls of half-inch-wide splicing-tape instead of the much-costlier-per-foot dinky little tape-rolls that you usually find included in tape-splicing kits, only to discover that most of the movies he liked were now available on DVD, and so he would seldom have a need to splice broken videotapes anymore.