@TheHappySpaceman
To be fair:
Extremely valuable is kinda inaccurate if you want to convey “having a really high price / is worth a lot of money.”
Valueable imo, means “it can be valued” and to value something is to set a price on it, usually on a give scale and against a reference, in order to give it a fair price.
Something invaluable means that its value is outside of said scale and it is incomparable against the references. It may or may not be, actually worthless.
Since you can’t appraise an invaluable object, the assumption is then, that it must be extremely rare and therefore of very high price, but nobody knows
how high.
Extremely valuable is therefore, I think, should NOT refer to highly priced and expensive items but rather on items that
can be valued by anyone, on any scale, in any market.