We are two people going to be traveling to Manali from Chandigarh, and will be staying there for three days then coming back. I need to find out how much the cost of the taxi would be including the three day stay and returning back.
A one way taxi would work out best for you and then get your own public transport within Manali itself. The cost for the one way taxi would be between Rs4000 - Rs5000.
Get a taxi from Chandigarh to Manali, then when you reach Manali hire a taxi according to your needs. There are plenty of other modes of transport in Manali as well other than taxis and you can even get shared taxis within Manali. I take it that you will be going sight seeing in Manali?