it may vary and very well could be dependent upon several factors. Authorized dealers recieve a better cost than a bootleger. Bigger volume dealers may well recieve better costs or at least some more perks than smaller dealers, like every 100th guitar free or some such..
You may wish to leave a few extra sheckles behind to cover his overhead and maybe even maintain the friendship.
Typically , not that long ago, most amps and guitars could be had for about 30% off of list. This left enough coinage for the dealer to make a profit and keep the doors open, feed people etc.. Peavey gear (I was told) was the exception as it was already budget priced. I do not know about the boutique type instruments.
The largest discount off of list I ever recieved was on an Ampeg Baby Bass, two were in stock and as I was trying it out, two more were delivered (great timing). I think it might have been around 50% off. The store owner was great guy and my extended family had been doing businees at that store since before he owned it. I needed a supper club sized amp and walked out the door with a new Ampeg B15S, no money down, no held check or anything. Simply a promise to get the money in their as soon as I could. He lent a DJ friend of mine a spare in the box new power amp and mixer to act as back up for my sisters wedding. My friends other stuff had just been serviced.
Best Of Luck
Wesley R.