These are worth a read,

https://www.amazon.co.uk/Where-Did-M...d+the+money+go

and

https://www.amazon.co.uk/gp/product/...t_bibl_vppi_i4


Basically you'll end up charging less than you should as there is always someone cheaper which you are competing with, but its worth knowing you are doing stuff too cheap rather than being a busy fool.