Raj Bhai.
You have asked me a tough question about Expenses per person and all. It will tough for me to analyse and come to any approx conclusion.
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However, it would be prudent If you meet up with a travel House/Office/Agent who handles Travel business for indivuduals and groups,gi9ve your programme and ask him for a rate.
Generally...
more... with the activity you proposed 2 FULL day stay is mandatory in Manali. One for Local Sight Seeing plus Kullu and Manikaran while next day for Solang valley and Rohtang Pass.
There are many hotels in Manali where DoubleB/TripleB Rooms are available from 700-1500.So plan accordingly.CAB fare with 18 seater might take you around 3.2-3.6k One Side drop.PLUS account for food Expenses and local Sightseeing CAB rates.
The overall budget must be around 5-5.5k approx per head.
However better to consult a Travel house and get a detailed rate with all your plans.