If you book via Monarch hotels you will have to pay now, or use a credit card to delay payment for a while. It adds 2.5% which, as I have good holiday insurance, isn't worth it to me.
Last year the Marinha Dourada were asking R3500, but if you haggled could possibly get it down to R3000. That's what they are probably asking now so it's a minimum of £43 per night. You need to get it down to R2300 to match Monarch's price which they no doubt negotiate by block booking lots of rooms then selling off their surplus. Last year, through Monarch I only paid £24 per night, annoyingly I paid £32 this year before the price dropped back to £28 ! With the rupee getting stronger year on year, Monarch are probably working on a deal agreed last winter.
I think the Nazri will be a similar position but be careful, they have two standards of room there , the new build and the old ones. I haven't seen them but reading reports there is a fair difference.
Of course, the beauty of going for 21 days and DIY is you can split your holiday and stay in two different places as we are doing if you so wish.