Speaker purchase question

I have been a member here for 22 years, but encountered something today for the first time and would appreciate your opinions. 
I bought a pair of used speakers on Agon and they arrived with no grilles. The seller is stating that the pics did not have grilles (true) and they were not mentioned in the ad. These Rega speakers did come standard with grilles originally. I thought that the pics were taken to show the condition of the drivers. When I asked the seller, he said that he had looked into buying new grilles, but since he didn't mention them in the ad, it should have been obvious they weren't included. 
Am I wrong to feel deceived? I want to be reasonable and would be interested to hear other opinions. 

Definitely seller fault so far as he didn’t mention on ad or description 
if he’s not willing to negotiate the replacement price then contact PayPal or your credit card 💳 company to return it so next time he’s going to learn 

"Am I wrong to feel deceived?"

Morally, most likely, no. Legally, based on information here and without seeing the original ad, yes. The default position of any used item being sold is "As Is" regardless of that being said in the ad or not.


If a buyer makes assumptions about the item being sold, he is also assuming responsibility as well should he happen to be wrong.

Some sellers will tell everything even down to the most insignificant detail. Whether it is intentional or just their nature, other sellers will say very little. Nevertheless a seller is only wrong legally if he lies or gives misleading information.

The seller operated in bad faith. 
Why? Because he knew that the grills
would be expected to be part of the deal
and he failed to mention that they were not.

Meantime the buyer violated the primary directive.
Ask about every detail in writing. Get pictures of
all surfaces not pictured. Assume nothing.

The fact that all you got taken for is a set of grills
is actually a lucky break for you. 

The seller did better than describe what you were buying, he showed you pictures.
speaking from experience, not every buyer and seller here are noble characters, to say the least