You answered your own question.  As with any gear, the value is in your opinion of it.   You like the sound? You going to use them? Then they are worth something.  More than likely more than you paid.  

Meinl has been making some decent percussion gear lately, Id be surprised if those arent some nice congas.

How many is in your set?
2, 3, or 4?
Wood or plastic?
Heads - cowhide or synthetic?

Are you playing conga songs with them, using them as percussion support in a band, or just messing around with them? Each one of those questions are equally valid and no bias is meant.

But, the type of drums you have makes a difference to others dependant on the situation where you're playing them.

And lastly, if you're not already an expert conga player, you should find the best teacher around and take lessons from him or her.
It'll change your perspective.