At the moment, a huge part (nearly all) of the bitcoin economy is made of exchange with other currencies, mainly USD. Just see how everyone's so worried about the future of bitcoin (sic) because the main exchange place was compromised. That tells a lot about what bitcoin means for everyone.

Taking your example situation now. If the only thing you could do with dollars was selling and buying them with your native/former/other currency (INR), you would need to take the exchange rate into account a lot when you see or give a price in dollars – because they would mean nothing else but INR at the end of the day.

As you say, the only way to get an independent notion of bitcoin's worth is by thinking about what you can buy with those coins you just received as a payment. This means we need to stop focusing on the exchange to get coins, and set up more goods and services, so that bitcoins can exist within their own ecosystem. I need coins? OK, I'll sell some goods or provide some service. Exchanging should only be a side solution if we want a sane currency.