I know that this is late for this Christmas, but I wanted to make sure that someone at least answered your question.
If you click on the following search, you will find links to sites that have similar items to yours that are for sale or have been sold. You might want to check out the information on the links to help you in determining a price. Of course, what something is worth in monetary value, does ultimately depend on what someone is willing to pay for it. I do know what you mean by "priceless," though. I have some baseball cards from the 1960's that I would just hate to part with in any way. But, we do what we have to sometimes in order to get money.
Sports Autographed Photo Brett Favre eBay - Google Search
Since I'm running short on money this year, I just went to a store and picked out a bunch of inexpensive items to give to people. Things that are decorative like candle things and ornaments.