Someone who buys cels to immediately resell them 
uses time to earn money by providing a service: 
making cels available to those with who have less 
time than money. 

Similarly, a collector who nabs a great cel from 
site _xyz_ does the same thing by trading time 
for money, at the expense of collectors who don't 
have the time to check the site very often. 

Regards,
Chi