While I am like most others in this thread that said, if no prices, I usually just walk on by...but I am also like you and am wondering why someone would take the time to setup at a gunshow and not price items.
One small show in rural Minnesota, many years ago, there was a table with nothing marked, there was a couple bullet molds I was interested in, so I asked the vendor, "how come you haven't priced anything?" He said it's all my late fathers junk, I just want to get rid of it and I don't know what anything is worth. I got the two Lee 2-cav molds for $5 for the pair...so I guess he wasn't lying.
Another time, Same show, different year. A table had a couple guns with price tags, but also three large boxes of misc gun related items...nothing priced. I asked "what's the deal?". He said people like to dig around in boxes...he said it's like looking for gold. So I look in the boxes and picked up a leather holster that looked like it would fit a 6" N-frame and a scope mount in the package to fit something I had. I ask the price, he said how about $1 each.
Lastly, and this is the best...At the local annual show I have a table at (for each of the last 20 years), there is a couple old guys (brothers they tell me), and I have become friends with them over the years. They never price anything. Everything they bring looks like it's been stored in a barn for decades ...they are old, so I wonder if they had some sort of gun business decades ago? I ask them for prices, they always counter with "what's it worth?". Since we are there all weekend, some of these conversations go on, and off, over both days. They usually want more than I am willing to pay. It is fun negotiating with them as a vendor, as it kills time during slow periods, but I would normally just walk by their tables if I was just a gunshow attendee. I watch them interact with customers, and they do sell some stuff.