Builling for design projects

Any ideas on how much to bill for jobs? Lucky break for me, no billing experience so far except freelancing…want to be professional and charge fairly, somewhere
in the middle, sure client has good budget.

ie. new cellphone. development/ 3d modelling/ presentation model/ final bling?
phase1
phase2
phase3

also how about interiors?

new cosmetics store.
display furniture
lighting
graphics
material specs
plans & modelling