My taxidermist charges $350 for a whitetail shoulder mount and then $65 for a wood plaque if I choose to have one (which I usually do).
I caped my first 3 bucks myself and enjoyed the experience, but now have the locker do it. They charge $30. It only takes them a few minutes to cape out and they do a great job.
I usually spend around $200 on a processed deer. However, we get large percentage made into summer sausage, bologna, deer sticks, and jerky. Kind of pricey, but we sure enjoy the meat. The locker I take my mule deer to in Arizona charges $50-$75 for the same thing??? Guess it kind of depends on where you are hunting/living.
Cardeer gave some great advice...take pics!! I recommend taking a entire roll of pics (24) for every trophy taken. Pictures last a lifetime and it's unfortunate the number of avid hunters I know who take 2-3 pictures and wish later they'd taken the time to take more[

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Best of luck to you and remember all of us had to ask these questions at one time or another! Hope some of this helps.
TB