In a way yes! You are paying both for the container and the brand name that guarantees your safety while drinking the water bottle. While water itself is basically free, there are a lot of processes and ways that water can be made drinkable. 

A lot of water bottle companies claims that their way of processing water into drinkable ones are the safest and the best way but unfortunately consumers have no way of knowing which one is better. The more consumers believe that one product is better than the other, the more that product can increase their price because the demand will likely increase. 

Aside from that there are also others who claims that they added a little something in their water bottles like electrolytes, which entices more people to buy the product because of it's added benefits.