My dealer has a new MY 2025 SL 55 with an MSRP of $154,000. What kind of a discount can I expect? I've noticed in these forums some have claimed substantial discounts. Just curious. Thanks in advance.

Dunno about dealers selling new cars, but I would think that finding one a year old with 10k miles might have depreciation and sell for considerably less. But, I haven't looked at newer ones, mine are 2003, 2004, 2007, 2008, 2013. But typically it is better to get one someone's owned a year, rather than new, although I also don't know how transferable a warranty is...LoL
You could go to that dealer and make offers, say 130k and don't budge, and see if they go for it, and if not, say well thanks anyway and walk out. They might stop you at the door? Worst they can do is laugh.