Thanks for the responses so far. Rising shipping costs are definitely another factor impacting buying and selling. Since the pandemic, USPS has raised rates a whopping 10 times. Not counting peak-season surcharges, Canada Post has raised rates 5 times during the same period.
While the US does not have a VAT-style tax, some online marketplaces (eBay, Etsy, Mercari, Discogs, and others) now calculate their fees not only on the item price, but also on the shipping amount, which in turn gets passed along to buyers.
Coin shows must be great for those who live near the venues where they are held. The closest ones to me are usually about 3 hours each away, so I haven't attended one in many years. If I ever make it to Toronto, I'll try to time my trip to coincide with a show.
I really balk at the fees charged by auction houses, but when I stop and think about it, I suppose there are acquisition costs no matter how one obtains collectible coins or currency, aside from those rare occasions where something valuable turns up in circulation or comes your way in an ordinary transaction.