I wasn't talking about using flash drives for backup purposes. You're better off using another hard drive for that (and possibly a set of optical discs every few months or so), be it internal or external. I was talking about porting individual utilities, updates, software installers, and bits of data like HJT logfiles, Unknown Devices logfiles, driver backups, DLL files, etc. (especially in the absence of a fast Internet connection). Flash drives are especially useful for students, and also for some office workers who don't have remote desktop connections.
For backing up large amounts of data, money is definitely an object. So let's put our money to work for us. Excluding online stores, where you have to wait and often pay shipping, one of the best deals you'll find on DVD+R discs at a physical store is at Big Lots!. You can get a spindle of 50 DVD+R discs for $9.99 pretty much anytime. In this case, excluding tax, you're paying about 4.25 cents per gig; this is assuming you use every last bit on each disc, and never burn a single coaster. The latter is unlikely, and the former is definitely not going to be the case.
One of the best deals I could find on a hard drive was actually not an internal drive, but a Seagate FreeAgent 1.5 TB external at Costco for $99.99. In this case, you're paying 6.67 cents per gig. If you want a whole 2 TB, a good deal can be found at Best Buy, in the form of a WD Elements 2TB external for $144.99. If you want to save a few dollars, you can get a Caviar Green 2 TB for $139.99. Here, you're paying either 7.25 cents or 7 cents (6.9995). Again, think of the money you might be saving on slack space and bad burns. Also, there's something else to consider...rewriting. Which brings me to my next point...
Unless your files never change, you're losing more optical disc space on duplicates. Needless to say, if you run out of space on one-shot discs, you have to buy more. If you would rather dump some obsolete files and rewrite, then you'll want to go DVD+RW. At Best Buy, you can get a spindle of 25 Memorex DVD+RW discs for $22.99. Here, you're paying a whopping 19.57 cents per gig, not to mention the extra time you'll be spending on disc swapping, erasing, and simply the slow comparative speed of optical vs. magnetic storage. And time is also money.
I still stand behind what I said before about using DVD+RW for pivotal images. After five uses, you will have made up the difference in price between rewritable and one-shot discs. But for everyday backup jobs, you can't beat a hard drive. Cheers!