Here is my advice... (This is coming from more of a sign shop slant, but it applies to any service business)
You need to analyze your entire financial structure. You need to know your bottom line so that you know what to charge.
The easiest way to do that is with software.
Here is what I use, and it makes life easier...
EstiMate Software
Sign Pricing Software | Sign Business Management Software | EstiMate
This software was originally designed for the vinyl sign business. It is an easy to use quoting system.
They have pricing plugins that you can buy (they are cheap) that include:
Vinyl Signs
Thermal Printing
Embroidered Items
Wide Format Inkjet
Screen Printed Signs
Screen Printed Garments
Flatbed Digital Printing
and the list goes on...
There are several ways to buy the software, outright, monthly and installments. One way or another it will fit your budget.
Back to my point... This software will help you determine at what rate, or how much to charge to make a profit.
When you first install the software it will interview you, and ask you all your costs, including rent, utilities and etc.. It goes into great depth.
Before installing the software make sure you have all your bills and costs in front of you, it will make the interview go quicker.
It will also ask what you want to bring home, and then it will compute everything you gave it and will give you a basic shop rate that you must go by to make a profit. That might not mean much at the moment, but then you install your Screen printing plugin/s.
When you install the plugin/s it will interview you again and it specific to the plugin industry (screen printing) to determine what to charge to make a profit.
Once all the configuring, the hard part is done, then the easy part starts...
You get a call to quote a shirt (providing you have the software running already) you just input the specifics into Estimate software, colors, shirts, sizes, materials, and in seconds it will give you a live quote to give your customer.
Built into that quote is your overhead, plus what you told it you wanted to bring home. This will help you make consistent profits, deal after deal.
Just to clarify, I am a customer of Estimate and in no way affiliated with them outside of that.
I have said it in other posts, I do not like accounting and book keeping, I try to keep it automated, and this software allows me to quote in seconds and know I am not violating my profit margins.
I do both vinyl signs and screen printing, so this software has helped me out tremendously.
If you don't have an accountant or a book keeper at least, I recommend you get one, don't spend your time doing something that will sap your creative energies, or take you away from the thing you do best, making money.
I would also recommend Quickbooks, Estimate software will export your quote into Quickbooks allowing you to bill directly from the quote, saving time and money.
I hope this helps...
DZ