If you read one of those huge articles, Arjun mk1 costed Rupees 21 Crores (3.3mil$) as of 2010.
Arjun mk2 would cost around 8-9mil$ a piece. Its half a generation advanced.
The cost of Arjun Mark II will not be known from Wiki article.
You should look for answers filed by DM in parliament. That is the only trustworthy source.
