Yes this is normal. You can't take myplan 99 base pack officially without any language topup/add on.That's why for TN/Chennai region they showing 165 because they including tamil/telugu etc regional topup.
For Delhi also Officially you can need to take any language topup/add on, but I think some bug in Selfcare they showing only 99.
Called up the customer care and changed my base pack from Rs 219 to My plan 99, ROI. Changed Royal TN HD of 170 to Max HD TN 225. Effectively I'm paying Rs 324 (Rs 99 + Rs 225) every month opposed to Rs 389 with the previous plan. Very happy now
Edit: Now I subscribed to Regional Tamil and Malayalam pack free of cost. Thats a sweet deal, which would have costed Rs 441 otherwise and thus I save Rs 117 every month. Even better south combo was available for free, but I chose Tamil and Malayalam.