Yes, there is certainly a value to IRCs. Some can go for hundreds of dollars. Or, for very common ones, for nearly nothing.
Unfortunately, there is currently no complete and up-to-date catalog for them.
For those of Germany and related areas, they are listed in the Michel Ganzsachen Deutschland (Postal Stationary of Germany) catalog.
Then there is the Catalogue Mondial Des Coupons-Résponse (World Catalog of Reply Coupons). Volume 1, covering countries from A to H (as given in French) was published in 2010, but volume 2, covering the rest of the world, has been coming out later this/next year ever since.
There used to be a couple of web sites that gave a very comprehensive overview of them, but they have gone away.
I, myself, collect IRCs from Norway, Germany and German related territories. And have accumulated a scattering from other countries. I probably have a couple of hundred all together.