Hello
I am going to provide you the detail information of the cost of smart card of the Delhi metro

Delhi Metro Smart Cards at a glance:

Security Deposit Rs. 50/-

Minimum recharge Rs.100/-

Maximum recharge Rs.1000/-

Returning charge Rs. 5/-

One Day Tourist Card
Rs. 150/-
(Including Rs. 50/- of refundable security deposit )

Three Day Tourist Card

(for unlimited travel for 3 days) Rs. 300/-
(Including Rs. 50/- of refundable security deposit)

I hope you will be satisfied from my answer if you have any problem regarding to it or any other thing then feel free to ask me I will help you out.