Your assumption is actually far off from being correct. Train fare in India doesn't necessarily depend only on distance covered. Type of train and class of travel are also key factors in determining the overall train fare. Moreover, don't forget that there are special luxury trains operated by the Indian Railways - which are far highly priced than the common Express/Mail trains.
The Maharaja Express currently holds the record for being the most costly train ride in India. It is a special luxury train operated by the Indian Railway Catering and Tourism Corporation that runs on week-long pan-Indian voyages. There are 5 different tourism circuits that are covered by Maharaja Express. 2 of the 5 circuits are covered in 4 days/3 nights, while the remaining 3 are for 8 days/7 nights duration.
Circuit 1: Treasures of India (4 Days/3 Nights): Delhi – Agra – Ranthambore – Jaipur – Delhi.
Circuit 2: Gems of India (4 Days/3 Nights): Delhi – Agra – Ranthambore – Jaipur – Delhi.
Circuit 3: Heritage of India (8 Days/7 Nights): Mumbai – Ajanta – Udaipur – Jodhpur – Bikaner – Jaipur – Ranthambore – Agra - Delhi.
Circuit 4: Indian Panorama (8 Days/7 Nights): Delhi – Jaipur – Ranthambore – Fatehpur Sikri – Agra – Gwalior – Orchha – Khajuraho – Varanasi – Lucknow – Delhi.
Circuit 5: The Indian Splendour (8 Days/7 Nights): Delhi – Agra – Ranthambore – Jaipur – Bikaner – Jodhpur – Udaipur – Balasinor – Mumbai
This special luxury train is equipped with all modern amenities to offer the ultimate on-board experience to the travellers as far as comfort is in concern. Live television feed, WiFi internet access, attached restrooms, lavish dining cars, spacious bars, VIP lounges and souvenir shops are a few of the facilities that the guests can enjoy on-board the Maharaja Express.
Four types of accommodation facilities are offered in this special train - Deluxe Cabins, Junior Suites, Suites and Presidential Suites. The most expensive is the last one - Presidential Suite. For booking a Presidential Suite on a 8 days/7 nights circuit, one has to shell out a fare of USD 23,700, which can roughly be translated to INR 15,00,000. That holds the current record for being the highest train fare in India.
By the way, Srinagar-Kanyakumari is not the longest train route in India. The credit for being the longest train journey (distance wise) in India goes to Dibrugarh-Kanyakumari route. Vivek Express, train no 15905/15906, is a weekly train that connects Dibrugarh in Assam to Kanyakumari in Tamil Nadu and it is currently the longest train route in India with a total distance coverage of 4273 KM.
The Himsagar Express (train no 16317/16318), which operates between Vaishno Devi (SDVK) in Jammu & Kashmir and Kanyakumari (CAPE) in Tamil Nadu, covers a total distance of 3787 KM and it is the second longest train route in India after the Dibrugarh-Kanyakumari route.
Regards,
Deb