The people can invest any amount, no matter small, because the profits percentage they would get would be the same.
And as the time passes by, people may invest or earn more according to their needs, because 1 BTC goal may be difficult but not impossible !
With the price of bitcoin this high,unless you are capable to investing one hundred thousand dollars you wont be able to make any mad profit,people really like to make some profit and it wont happen if you are investing small amount of money,but if you really like to ride the rally then any form of investment will make you a profit.