It's my understanding that plate and chain armor weren't really contemporaries. Sure, chain was used to protect the joints in the plate armor, but I don't believe it was used for full suits anymore at that point.
What would the relative costs of the two armor types be? I know chain was very labor intensive to make, but would it be more expensive than plate?
As an aside, this page has a lovely photo of a 'Kabardian in military clothing' (from the NW Caucasus) in the late 19th C. http://englishrussia.com/2013/06/21/inhabitatnts-of-the-northwest-caucasus-at-the-turn-of-the-xx-century/ I wonder if this was just a 'traditional' or ceremonial costume, or whether mail was still being worn for protection in combat.
To be entirely fair, plate armour definitely didn't eradicate the use of chainmail, by any means, however, it did reduce the use of it. While both armours were physically exhausting to wear, chainmail did let the skin breathe a little more, due to the rings. Plate mail was easier to make, as you only needed to hammer out a sheet of metal, while when making chain, you had to painstakingly rivet together every little chain. However, the stopping power of chain was more or less unrivaled until the invention and widespread use of the firearm, and even then, was still strong enough to be used as a secondary means of protection. Was chainmail still used for full suits? Definitely, but it would have been rare to find a full suit that had been recently made. After the introduction of plate mail, they would usually only use more or less undershirts of it, which would protect the joints. I did, however, find some reading that might interest you if you continue to ponder about chainmail, and need some reading material.