The cost of a rainwater tank will depend on the size of the rainwater tank you're installing.
Some larger tanks will cost more than smaller water tanks and the tank cost is the largest costs of the install of the rainwater tank.
Some smaller rainwater tanks can cost as much as $800.00 to $1,000.00 while larger tanks could cost from $2,000.00 to $3,000.00
Then if you pay someone to install the tank that's usually another $200.00 to $500.00 depending on who does the work.
Usually installing just a rainwater tank yourself is pretty easy and you can rent a track hoe to lift and move the rainwater tank into place for pretty cheap.
Then you just plumb the rainwater tank into wherever you want to plumb it into.