1 btc is equal to 1 btc... irrespective of usd price of btc...
If you holdling for long term, you dont loose and you dont gain... because 1 BTC equals 1 BTC
That's irrelevant, he wants a computation on it.
Buying $100 worth of bitcoin @$10,400 will give him an estimate of 0.009
BTC and let's say it moved up to $11,000 his $10,400 worth of bitcoin will become $105 so the profit is quite low if he only holds a very small amount of bitcoin.