Aloha and welcome! :wavey:
Just to clarify, you're looking for advice on how to value your pins, not actually sell them, correct? Here's what I would do, and it may or may not seem a bit strange:
I would turn to Internet sales sites like eBay. Yes, this might take a while, but it's really the best I've got. I would look up each pin on eBay (or equivalent site) and find the selling price(s) for the past month or so. It doesn't matter for what the pin was listed, what matters was for what it sold. If you need to expand the search past a month to get a solid mix, or even one sale, that's fine.
Once you have your selling prices, I would discard the highest and lowest prices as outliers (unless they're very consistent with all selling prices) and average what is left. That average becomes your 'fair and ideal' asking price, whether in cash money or trade value. The remaining high and low is your high and low range.
I hope this helps. Please don't hesitate to ask if you have any further questions; I'm sure that someone (or several someones) will be more than happy to answer them for you.
