Does anybody else find this practice irritating...?

Yes! VERY!

It's a business. For anyone defending the work or effort to price 2,000 items, when was the last time you went into a store? Do you buy things with no prices on them or do you shop? Do you ever find yourself buying something that you didn't intend to buy, because it was attractive and at a good price?

If I see something and it's "a deal" I may be tempted to buy it on impulse. If I shop a flea market or even rummage sales and see no prices, I ignore that booth or sale and move on. I don't bother looking.

Dealers can put small color dots on things if they don't want to write prices in pencil on everything. Market goes up, all dots go up. Item goes down, new dot.

Maybe I'm just getting old and crabby myself, but I'm tired of asking "how much for this?", "how much for this?" wait while they deal with someone else "how much for this?" It's like I'm waisting the dealers time that they could be spending on other customers who might have more detailed questions.

Want more sales? Put clear prices on everything, or at least throw it in a bin marked "everything in this box $" there are a bunch of ways to get around re-pricing for every event.