From what I saw in Doha you can pay 500 to 3000 per month for a child in a nursery,all depend what quality of service your are expecting, how experienced is the staff, how clean and organized is the place, how many hours a day you need, if food is or not provided, how many kids per teacher, the activities they are offering and the name (those generally have waiting lists).
See what is your budget, check the places within your budget and select the one you like (or consider increasing your budget if you are not satisfied by what you found in the 1st place).
Good luck!