Bonjour Stuart ! That's an interesting case! Indeed, "une valeur sûre" could seem to be a possible synonym here for "une valeur certaine", however they don't actually mean the same thing in French. ​ ​Look at this sentence: "Fais-moi confiance, c'est une valeur sûre !" (Trust me, it's a safe bet / a sure thing / a valued asset!) ​Note that you use it with "être", and would never say "avoir une valeur sûre". I hope that's helpful! À bientôt !

Bonjour David !

I looked at the examples you provided and:

On a une valeur sûre avec Lisa Angeli.  
-> Here it's the same case I mentioned, where it means she is a reliable talent for these people. This sentence means that "they have a reliable winner in her."

As for the other examples, I must admit that they seem valid, though I've never used this expression like this myself.

I will therefore amend the question to accept both answers :)

Merci et bonne journée !