what does 'pack of 3' mean? does this contain 15 meals or just 5 meals?

One pack has 5 meals. This has 3 packs in it. So, yes there are 15 meals.

How long the expired date? still how long?

In my case, the date is Sept of 2021, lower right hand corner of the back of the box. That said, it is a pointless date, like putting an expiry date on aspirin. The noodles last for many years and the flavorings are pretty non perishable. I think they have the dates for inventory management rather than consumer use.

So this is about $6 a meal? For dry noodles and broth where you add water and meat and condiments? Can this be right?

You don't add water, you boil the dry noodles in a pot of water like you would dry pasta for spaghetti, and like a pasta dish you make at home, where you add ground beef and pasta sauce, some parmesan, and basil, you can add toppings to the ramen noodles and broth. I add my toppings to make it 'ramen'. Fresh vegetables, sliced beef or pork, nori, sauteed mushrooms and spinach, 6 and a half minute boiled egg. How does it compare to Top Ramen or Sapporo Ichiban or any other cheap ramen? Night and day. I don't eat that kind of ramen anymore. .50-.75 cent ramen? Unless you're penny-pinching, sure. Better quality noodles, best quality broth pack, pork/bone base liquid with pork fat. I've seen it sold for nearly $10 per serving at some places so $6 isn't bad for the taste. So far the best I've been able to find and I have tried many different brands of fresh frozen or dry type ramen. Can it compare to ramen at a restaurant that can cost me $13-18 dollars a bowl? It can come close and can be better than some other restaurant ramen that I have eaten.