I got the price down to $150 because I told them that I am not getting married at RIU Palace and the Renova Spa does not offer airbrush make-up. RIU will be sneaky and they will say that it is $150 per person. However, I have an email from RIU sales department stating the $150 vendor fee.
Besides my email correspondence with the RIU sales department, I have my travel agent also email RIU properties, I was using the group booking as leverage to get any discount or promotional offers to be added to the group booking. I always emphasized on my email that I have 85 confirmed guest and that I provided great profit on RIU on the slow season.
Are you getting married at RIU? If you are, it will be hard to negotiate the vendor fee. If you are getting married at RIU, are you getting any incentives, like spa discount, upgrades on your room, or semi-private dinner for your guest? Another way to save money is refunds from the hotel properties, have you done any research for group booking?