I know just getting some grapes and strawberries isn't going to make it worth the price per pound as you can get a whole bag of grapes, perhaps two for the price. So what I've seen people do, is they fill it up with lots of meats and eggs and cheese. Though, I still doubt that is enough to make it worth the price per pound.
Heck, I suppose my question is, can you EVER make it worth the price per pound?
In short, it's unlikely (although I don't know how much your salad bar costs.) You're paying for all the meat and cheese that goes bad after sitting out all day (or having some kid stick their hands in it after licking their fingers.) It's convenient, but it will always be cheaper per salad to buy the ingredients and make salads yourself. Or just buy one of the prepackaged salad kits from produce if you want something single-serving.
Ah, not to mention flu season. People with runny noses wiping their nose with their hands, never washing them, and then putting their hands all over the salad bar. Just disgusting.
It's worth it if you only need a small amount of something and you know if you bought a whole package of it, you would end up throwing the rest of it away. A bargain isn't a bargain if you don't use it.
The crazy ones I see are the customers who will get a whole large container of just the iceberg lettuce. They could get a full bag of the same already chopped lettuce for less. That's still getting the convenience of not buying a head and chopping it themselves.