Please explain the difference between "valued" and "valuable" when talking about goods. Which of them should be used to indicate intangible value and which to indicate price? For example, if a product is very useful and inexpensive, is it "valued" or "valuable"?
Valuable means something is likely to be valued by a lot of people.
Valued means it's definitely already valued by some people.
If a product is inexpensive, it may be valued by those who own it, but it can hardly be valuable.
Typical uses of valued are:
The item was valued at $5000
… which means that it was judged to be worth $5000.
He was a valued member of the team
… which means that he was a useful member whose value to the team is appreciated by others.
Typical uses of valuable are:
It was a valuable item, being valued at $5000.
… "valuable" here meaning worth a lot of money.
He was a valuable member of the team.
… meaning pretty much the same as before, except that there's no implication that others appreciate his value.
I disagree with the accepted answer, by @Ricky.
I would say that a thing that is valuable has value. It is not that it is "likely" to have value or that "many people" have valued it. It is enough that it has value for one person for it to be valuable to that person.
See the examples given in the answer by @ralph.m.
Adjective: valuable val-yoo-u-bul
Having great material or monetary value especially for use or exchange
"a valuable diamond"
Having worth, merit or value
"a valuable friend";
Adjective: valued val-yood
(usually used in combination) having value of a specified kind
Held in great esteem for admirable qualities especially of an intrinsic nature
"a valued friend";
-"This object looks valuable, I wonder how much it is worth." -"I'll tell you, it is valued at £20."