I'm sure that Todd Huffman from Birdman Studios doesn't ordinarily have shot birds that he displays as his studio pieces. That bird is definitely mature, but more than that, it's just in better plumage than locally harvested birds typically are. Just due to the fact that our season dates end in January at the latest, (early December here) while a farm raised Ring-neck like that bird there, was probably put down for taxidermy purposes in the month of March or April. Cost? Anywhere from $150 to $300 depending on the quality of each and every feather. I will also tell you that you should be very pleased with the plumage of your three-bird display of your Ringers as well, and if I haven't told you this before, than here we go again. Your mounts look fantastic. Especially for the fact that you aren't pursuing this as an occupation.
If anyone wants to purchase any great looking birds like that for a display, or just for the fact that you don't harvest a particular species in your state, I have a guy who raises nearly any species of waterfowl, from the not-so-plain Wood Duck all the way to Harlequin or King Eiders. As low as $50 for the Woody, and upwards of $2500 to $3000 for the Harlequin and Kings.