We love parts on reels. Who doesn't? But reels aren't always practical - and it's not just about cost. Cost is, of course, important, but there may be other factors to consider.
Say, for example, you need 20 2.2K Ohm, 5% 0805 resistors. You could buy a small strip of 25 from Digikey for $0.32. That gives the 20 you need, plus a few spares just in case.
Alternately, you could buy a digi-reel ( a custom quantity reel). On the reel, you'll probably want more parts to keep the strip long enough for the feeder. Let's go with 250 parts for $1.39. Digikey charges $7.00 extra to create a custom reel, so that's a total of $8.39. Still peanuts.
For a third choice, you could just buy a full reel of 5,000 for $10.64. Still peanuts. If you're gong to need the same part for a lot of designs, this might make sense. But, there's more than just cost to consider. You need to store and ship it. Shipping two dozen reels gets pretty expense. Storing and inventorying several dozen reels can become a hassle too.
The beauty of Digikey, Mouser, and other places that sell cut strips is that they essentially become your parts warehouse. You pay the $0.32 cents and never have to worry about whether the part is in your inventory, how many are in your inventory, digging it out of wherever you stuffed the reel when you last needed it...
If you do buy and store the whole reel, you don't need to ship the entire reel to us. Just cut a strip with the number you need, plus about 5% for that "just in case."
Of course, if you need a few thousand of the parts, go ahead and send us the reel. It would make sense then.
Reel, reel your part
Solder it, solder it, solder it, solder it
Cost is but a factor