Dear Brian,
Actually, the cost you'll pay depends on location (old city or left bank), flat condition, furniture, transport access and due to the climate the building itself. Many landlords also pay attention whether you have family and children or move alone.
Generally, the right bank of Astana (old city) has developed infrastructure - lots of stores, banks, transport and entertainment areas. On the contrary, the left bank is the place of offices and government structures, where everybody works, not too much restaurants, some traffic jams at peak times, more expensive service and living. When searching for an apartment I would recommend to pay attention for the next: location, transport (how easy and how long will it take to get your destination) and if its warm in winter, because the climate is sometimes very tough.
Average rent for expats and foreigners are usually higher than those for locals, due to the necessity of owners paying agents fee in amount of first month rent. If you know your office location or preferred living quartiere in Astana and preliminary budget, please let me know, I could advise the average price from the owner.
Best,
Kadyr