Tiny Towers - Help

[jas22107]

my average sale per minute is about 600 and if I'm extremely lucky it goes up to 1000 for a little while.
Currently I have 14 of each type of commercial floor and 33 residential.
floors. About 75% of the commercial floors each have 3 dream job employees
should the avg sale per min be higher?? am I doing something wrong? It's taking me like 3 days of playing it numerous amours per day to build a new floor!