Like Holly said, and what follows much of what you'll read in "how to" books on the photography business, your prices are based on your Cost of Doing Business. The complicated answer is research this, use the
calculators such as that offered by the NPPA, and do your best to figure out what you can and will earn versus what you project your overhead to be and then add a living salary onto that and you know what your time is worth. With that, estimate time costs to you for each job and then price accordingly.
Simple answer, look at your local competition and charge the median. Judge your skills and marketing efforts versus theirs and adjust higher or lower accordingly.
My prices, service versus prints, may be changing soon. I've found that I do just as much business as I raise my service rates, but the market "did not bear" my on-spec sports print prices last year, so I'll likely be lowering them soon. I'm finding my small business clients earn me a greater and more stable profit than my non-commercial customers.
Best I can offer beyond that is keep track of your own numbers and over time, adjust accordingly; maybe pick a median now, see how you're doing six months from now, and then adjust accordingly to either do more business or earn more profit - or even better, both.