For Rio Grande do Norte it really depends on where in the state you are looking to buy:
The value of the property of course is linked to the size of the apartments and build quality, amount of leisure areas, on-site facilities, location and accessibility. The further south you go from Natal, normally the cheaper the units as the further south you go the less infrastructure you have in the surrounding neighbourhood. This is of course until you reach certain tourism destinations like Pipa and SMG.
Prices in the city centre are going to be very different and again depends on the neighbourhood you are in, but here are some ideas of realistic prices on the southern coast between Piúm and Barreta (first village after Natal to first village before Tibau do Sul / Pipa)
3* - from R$ 1.400,00 per m2 to R$ 1.800,00 per m2
4* - from R$ 1.800,00 per m2 to R$ 3.000,00 per m2
5* - from R$ 3.000,00 and up - no real limit - if it's special, Brazilians will pay for it
Your quotes were
£1200 per m2 for a 3* star resort = R$ 3.306,00 per m2
£1400 per m2 for a 4* star resort = R$ 3.855,00 per m2
Of course the value of a property is what someone is willing to pay for it - so each development and prices need to be looked at on a case by case scenario. But just from those examples, your prices seem very inflated.
As for getting £250 (R$ 700,00) per week to rent an apartment in a 3* development - that seems very unrealistic - probably closer to that amount per month.
As for NOC - it seems to be the real first five star development in the north coast of Natal - if they do all they seem to be doing and manage to achieve it, it may well be the first five star development in the state, and therefore is appealing to a niche market - and will probably be very popular with Brazilians. Their prices are not cheap but I believe that is on purpose - I don't think they are looking to cater to people who are on a limited budget.
The location is isolated (a good thing in my view as the last thing you want near a luxury development is a bunch of mudhuts) but there is a lot of promise for the area - nearby there are plans for another luxury development and the village near the development is quite cute. It's the first I've heard about US$ 400 per night - that seems quite high to me, considering prices of five star luxury hotels in Europe and the prices of hotels here in Natal, but if they can achieve that, all the better. I think their main challenge will be the zero-based staffing of the hotel due to the existing labour pool. However opening hotels is a very challenging process and that is only one of the very normal challenges they will face.
There is a little pousada on a surfers beach in Ceará which charges more than US$ 400,00 per night and is doing so well they are looking to open another hotel in the state of Rio Grande do Norte, so it is certainly possible...