Chances are the more teabags you get in a box for the cheaper amount is because it's simply that... cheap tea. Usually the leftover bits of leaf tea (we actually call these "sweepings". I'll let you guess why). If you are in the states the best to get is Twinnings unless you find an actual proper tea shop. Don't be fooled by the cheap British standards such as Tetley, PG Tips, or Typhoo. They have been around for ages and there's a reason they are "economical". Leaf tea is always the better way to drink tea as it retains much of the proper goodness. To put leaf tea in a teabag you have chop the tea leaves and it destroys much of the properties. To be honest with you, I didn't have a clue about tea until I moved here and started working at Whittard's. I didn't know there was a whole world of tea and coffee!
The strength of tea depends on what type it is. A black tea will always be the strongest. These are usually a basis for the traditional teas such as English Breakfast, Earl Grey, Darjeeling, etc. and often have flavours add to them such as Peah, Strawberry, or lemon and Bergamont Oil. China teas are usually a bit lighter in taste and green teas are often the lightest tasting. Teas such as Camomile, Peppermint, Raspberry and Peach, Lemon and Ginger are in fact, not actually teas. They are often called an Infusion or Fruit Infusion because they contain no tea at all but rather herbs, fruit bits or plants or flowers. They are most often than not always Caffeine Free (so ok to drink while pregnant!) and good for you. If you want to make iced tea over here the best to use are Ceylon or Orange Pekoe. You will find that most american teas use this type of tea as the tea for iced tea (does that sentence make sense?) I prefer using Orange Pekoe for iced tea because it has an natural sweetness already to it. Happy tea drinking!