UK is not part of the Schengen zone, therefore you will need to get two separate visas - one for UK, the other for Schengen countries (France, Germany, Italy, Spain, etc, etc.)
As an Indian national, a student visa for UK (under 6 month duration) costs 8715 rupees. You are also likely to pay a service or processing fee on top of it.
You need to apply for Schengen visa with the country of your intended first entry. For example, if you plan to visit France, then Germany, then Belgium and from there by train to UK, then France your first point of entry and you need to apply with the French consulate or embassy. The cost of a standard Schengen visa is 60 euro (if applied from India, you'll need to pay in rupees - about 4850 rupees at today's exchange rate). Again, you are likely to have to pay a service or processing fee on top of it.
There are no combination discounts of any sort, as the two are completely unrelated.
As for the travel cost from Paris to London, if you book in advance and travel off-peak, you can get a train ticket for about 40 euro if not cheaper. However at peak times this can go as high as 200 euro. If you want to take the ferry, you'll need to first get to Calais or Dunkirk (other French ferry ports are too far from Paris anyway) - and the actual ferry passenger-only ticket (i.e. without a vehicle) is quite cheap (a friend of mine got one for 10 euro last year).