If you've never been to one you dont know, but its like once you fly first class u wonder if you'll ever be able to fly coach again.
First of all, they have everything you need (or might need), and it just makes everything about your flight more convenient and comfortable (even if your flying in coach). Its basically one of those things that if your already on top of all your arrangements, its not so necessary (kind of like a black credit card), but if not (if your a bochur) it makes a world of a difference. For example, need a computer (or a comfortable/decent place to use yours)? hungry/thirsty? (they usually have fruit (which is kosher))(and that's besides the mashke), and in general its just very relaxing, especially after a long flight, connection, whatever, and obviously you can arrange all those things yourself and it will cost less (just go buy a coke for $2), but here, even though you might not drink your money's worth in diet coke, its the idea that anything you need they have and are waiting for you to utilize, making each shot of glenlivet בלי גבול. which brings to #2...
B. In general with travel, better service is not necessarily something tangible, meaning waiting in a shorter line or having someone take your jacket for you or in general being treated like a human being, while there is not necessarily a specific price tag u can give, is worth a lot. For example, have you ever traveled by bus? You feel much more like a human being on a plane and even more in first class (or at least in a lounge).
C. And most important of all, something very tangible and irreplaceable, when you get off your six hour flight, in coach, and you take a good shower (while everyone else is waiting for their bags), i think on that you can put a pricetag (maybe even the one they put...)
Anyway... sorry for the long post, a little bored here, but thats just my opinion, i think its close to being a necessity.