Is it my imagination?

Yes it is arbitrage. I would think it is usually the other way. eBay seems to get higher prices most of the time if it is a well know brand. Rotel, B&W, NAD, MSB, Adcom, Nordost and high end Yamaha, Marantz, Onkyo, etc.

I've actually had dealers buy my used gear; and then it shows up on their website's used/demo page at more. The dealer usually offers a warranty on used/demo equipment, so they can get more $$, especially from walk-in customers. One in particular was a vintage 80s Cambridge Audio amp, back when they were still made in England. The dealer was a Cambridge Audio dealer. I think he was interested in comparing it with the current stuff. He sold it later. The rest were mostly Tuners.

I agree with the points made, and support the mechanism of the free market. On the other hand it misleads buyers who make offers in good faith and are either mucked about while the auction concludes, or stood up when the eBay bid price closes the margin. Personally I would post feedback if I believed I was misled in this way, simply to let others know that they should be aware of the seller's lack of authenticity. Free markets operate better with better information.

Actually eBay frowns on people who run an auctions and have it listed for sale elsewhere. They've delisted people for ending auctions early because they sold the item elsewhere.
Advertising an eBay auction elsewhere is OK, I am referring to a regular classified that does not disclose it is on eBay.

...that's exatly the way...

Welcome to the internet!
It should come as no surprise that great buys on Ebay end up here. I recently observed a BAT VK500 amplfier sell for $2125 on Ebay that is a tough find below $2500 here, and also observed a real steal on a BAT VK200 that went for $1200, which are a tough find below $1600. If the market wasn't so volatile I'd have acquired both of those pieces just to resell, but times have changed since I used to buy and resell. There was a time not long ago that I upgraded my entire system at no cost to me simply by buying a piece here and there and reselling it. I must have made over $15k profit over a 6 year period. But of course all the profit was absorbed back into the system. The internet was good to me for quite a while. I've since moved on from the hobby, and have sold off most of my former gear, but it was fun while it lasted. I know of several audiophiles that have done, or are currently buying/reselling/ profiting from used audio buys. Dealers do it, so why shouldn't the average person?
I agree that Ebay prices are generally higher than can be found elsewhere, but if you keep an eye out regularly you can find an occasional steal! I think the best price I ever scored was a $1700 asking price for a Pass Aleph 5 amp and Aleph P preamp combo. Of course both pieces sold to Audiogoner's for regular market prices. And it would not surprise me a bit if both of those BAT amp steals I just mentioned didn't end up here on Audiogon! There's no shame in buying and reselling. Half of the fun in this hobby is buying a piece just to bring it in and trying it out in your system for a while, and then moving it on the internet at a profit later on. This would not have been possible to do ten years ago, but now that the internet is commonplace why not take advantage of it...especially if you live in a smaller area with limited access to high end retailer's. But as always, buyer beware.
Enjoy!