Yes, of course, "is valuable" is a two-place predicate... in principle, it's meaningless without specifying an agent who judges value. "Valuable to whom?" you might ask... "Me? You? Lemurs? Aliens from Alpha Centauri?"

Similarly, "is poisonous" is a two-place predicate. Poisonous to whom? But in practice, I can say "X is poisonous" without any difficulty, and people understand me to mean "X is poisonous to typical humans".

Similarly, "X is valuable" seems to unambigously mean "X is valuable to a typical human. So when you say you don't know what it means, I have difficulty taking that claim seriously.

For example, I am pretty confident that a typical human values an additional year of happy, healthy, pleasurable life. I am pretty confident that a typical human doesn't value losing a year of happy, healthy, pleasurable life. On that basis, I have no problem saying "an additional year of happy, healthy, pleasurable life is valuable," and I don't think that statement is vague or ambiguous at all, as I said in the first place.

I don't know whether we disagree about that, since you didn't answer my question.

Of course, I could be wrong. Maybe a typical human doesn't value an additional year of happy, healthy, pleasurable life. But even if that's so, it's still not vague or ambiguous, as you suggested initially. It's merely wrong.

WRT masturbation, I'm not nearly so confident, but if I had to guess I'd guess that a typical human values it... in other words, that it's valuable.