If you are familiar with the Priceline and Hotwire bidding sites and this property has had rooms come up - either now or in the past - I would take that rate vs. the current lowest bookable rate for the entry room type — and then apply that discount percentage to the suite.

i accidentally did this many years ago when I moved to LA. Negotiated a month long stay at the Hilton LAX and the hotel let me use a low employer rate (even though I was leaving that employer and my new employer’s rate was not quite as good), and they upgraded me to a larger corner room, installed a fridge for me, waived parking, and gave me Diamond benefits even though I would not earn them until 2 weeks in. I was happy.

But then I had a few 1-2 day stays because I was traveling back to the east coast (where I moved from) and then a few work trips - before needing another month+ stay. Since at that point I was paying out of pocket, I did Priceline and first ended up with the Sheraton LAX at less than half the Hilton corp rate - while still getting my SPG status benefits. And then the Sheraton mistakenly gave me a bill with the Priceline rate they received - which was another 10-15% lower than my bid. I then bid that even lower rate for the second Priceline stay and I got the Hilton — now about 60% lower than what I paid before, which was itself a really good corporate rate.

I was planning to go back to the Hilton for my second month+ stay, so I showed the manager the two rates and we worked something out for basically the Priceline rate - maybe a few bucks more than the lowest, but still less than half what I paid for my first stay there. And I got an upgraded room on top of that and full benefits. This was 17 years ago - so there may need to be more give or negotiation on rate for benefits and points - but still if you can figure out from available info what the lowest rate they will fill a room at, you have your starting point.