I called, and then visited Will bikes yesterday. They have some good helmets, but running a little low on stock, they said they'd get new supplies in a month or two. Prices start around 9k for Taiwanese Index helmets, and go up to 35 or 40k. I didn't see a difference in build quality of finesse though, and even where prices varied massively it seemed to be due to brands.
I didn't spend das lakh on the bike, only spent a little over one lakh(Ravi Piaggio 125), wanted to get a decent helmet to go with it. 20k is a bit over what I'd like to spend on the helmet though. I'm planning on going to McLeod road on the weekend, will check Xtreme sports out as well.