It takes 4 hours to reach Agra from Delhi. You could book a cab. You could book cabs via MMT or Goibibo. Cost is based on vehicle type you choose to travel. Basic cost starts from 2.5k.
It takes 4 hrs journy by yamuna express highway, by numbers of cabs available from airport and also from railwaystation, mostly they will charge 3k to 5k based on the vehicle u required.