First the best time to visit valley of flowers between second have of July to first half of September because u will find valley full of flowers during this season.
Reach to haridwar or dehradun as per your convenience then hire taxy as per your group. From there innova will charge you almost 5000 to 6000.
Valley of flowers have no accommodation and I have to come 4 to 5 km down to stay and there I was charged 800 rs for 5 candidates in a dormitory.Dude from haridwar 10000 is more than enough for 5 candidates collectively.
One advice, hire guide which charge you around 800 but it will be very informative. Visit this site to learn more.