4e is pretty predictable. Basic +1 items with no bells and whistles are level 1, 360 gp (and won't even drop as treasure, the lowest you can get is level 2). All the other +X items follow a predictable scale, being five levels higher and 5x the price, so a basic +2 sword is 1,800 gp.
A +1 item with just a little bit more is level 2 and 520 gp, whereas a +1 item with a daily power is minimum level 3 and 680 gp. In each case, it follows the same progress: 5 levels higher and 5x the price. So a +2 item with a bit more is level 7 and 2,600 gp, and a +2 level 3 item with a daily power is starts at level 8 and 3,400 gp.
That's the bit everybody knows. What I eventually figured out is there is also a pattern for daily powers. A daily item on any magic item is equivalent to an encounter power of a particular level. So I could take a level 1 encounter attack power from any class, reflavour it (or not), and make it a daily attack power on a third level item. The pattern here is that at each stage where you get an encounter attack power, the item equivalent will be a half-tier higher. I expect that makes little sense, so here is an example. The next level where you get an encounter attack power is level 3, and the next half-tier of magic item would be level 8, so a level 8 item's daily power is equivalent to a level 3 encounter attack power. So items at levels 13, 18, 23 & 28 would have daily powers equivalent in power to class encounter attack powers of levels 7, 13, 17 & 23. Utility powers follow a similar pattern. There are some quirks, but that is the general pattern. Basically you get a daily use of an encounter power that is decent enough to see play.
Consumables are universally overpriced for what you get, ensuring they rarely see play even if they are a found item. A consumable of a certain level is priced at (I wouldn't say "worth") 1/25 the price of a permanent magic item of the same level (a bit more for the first couple of levels, which compounds the problem). Consumables generally have a power level a bit (or more than a bit) less than an at-will class power used by a character of the same level. That usually makes them worse than every other choice available to a player.
Which is a good example of how supply and demand works in the metagame economy. You can charge more for an item, or an entire category of items, than players are willing to spend.