So if my maths is right you are charging them around $75 a week to clean the building ?

If this is US $75 it equates to about $150 NZ a week – for a building this large – if you are required to do all rooms I would say they are getting a very good deal.

I would suggest you ring around a couple of commercial cleaning places – anonymously ask them what they would charge for this size job – just say you are considering getting in cleaners but want some sort of idea on price first – you may find you can actually charge more – it is a big job.