as far as the paint mixing goes then in most places with there own mixing gear then thats the norm, using your colour code they can get the mix for it and mix it themselves, if you were perhaps doing the spraying yourself at home for example then you would go to a paint supplier and they would do it the exact same way.
Why only half front bumper respray???? would be just as easy to paint the full bumper..
the place i use for me painting would probably charge £100 per bumper, £180 for both skirts,£60 for wing mirror then whatever for the dents (cost on these is down to prep/repair costs/time and how much paint etc is required to blend the repairs back in).
other factor is the time it takes to prep all the items.