One Bitcoin will always be one Bitcoin. Maybe the the question should have been how much will the person had made if he had held the coin till date. But he would have have more Bitcoin if he had sold when the price rose and re-bought when the price dropped. Maybe op should have thrown more light on this topic.
OP was just simply confusing the whole thing, question should have been what was the fiat equivalent then and what is it now to been able to get the amount that he has made from that time to now if actually he has held up to that same bitcoin, because one bitcoin will forever be equivalent to one bitcoin that’s where its store of value comes in. But the fiat equivalent varies due to increasing value of bitcoin through the increase demand. One bitcoin in the year 2015 has its highest price at $465 that’s a 247x profit made which shows the increasing value of bitcoin and devaluation of the fiat currency.
As for if he had actually sold and bought back he would have made more, I think that depends on how he handle the market, because there have been many who have actually had 1 bitcoin and while trying to use this medium to make more bitcoin they end up having less of that bitcoin because of buying and selling back at the wrong time.