How much discount typically for a new MC275 to expect from a dealer?

I doubt you will be able to get any discount.
You might find a Dealer that will generate a phony trade in allowance on the sales receipt.

I know a dealer who is willing to haggle a bit on McIntosh gear but that was for one of the turntables and in a scenario where they were going to take off the stock cartridge and I was looking at a $10K pair of speakers.  They were willing to give me 5% and 90% of the value of the cartridge. 

Another dealer I talked to showed me the list and said that is the price.  They wouldn't even give me free shipping. With a brand like Mc who will pull the business if they find out a dealer is discounting nothing is likely discount you will get  If that dealer sells a lot of Mc gear, I am certain it will be nothing.  Be prepared to pay retail.  

You usually have to have a sales history with the dealer to get a discount.

Thanks for advice. I just may have to pay full retail. I’m always afraid to buy expensive used equipment. 

15% is about max I have found ,if buying 2 or more pieces a bit more .
from my McIntosh experience in the past.  You have to spend time shopping around .