A topic that always leads people in every number of directions.

The first thing that needs to be said, is that whatever your markup, you must include the cost that enables your business venture to grow, and expand - otherwise you'll just be covering your cost of living today.
The most talked about subject is the cost of 'inks' and the shipping cost... "lets use mugs for our figures, since these are 'heavy' item when having to purchase a box of 36" one mug is $1.05 (but you have to buy the box = $37.80) + shipping ($32.00) = cost on one mug $1.94 blank This then retails at around $14.00 each x 36 = $504.00 printed Ink (this can be very vague and change with each design printed) one cart $72 and perhaps prints at least 500 sheets = Ink cost $0.14 per sheet.... let's exaggerate! and say full colour $0.50 per sheet sublimation paper + shipping $47.18 for pack of 110 sheets = $0.42 per sheet blank. (this we can fit two mug designs to a sheet ($0.21 sheet cost per mug)) so we have mug $1.94 / ink $0.25 / paper $0.21 = One printed mug cost $2.40 to make. this means a box of 36 cost $86.40 to print BUT retails at $504.00 meaning a 'profit' of $417.40 on 36 mugs printed and finished! "Now why is shipping a huge concern to you?"
Since we do know that we will sell a whole box of mug during a period of time, it then is no problem having 36 on hand - we can then supply the customer a finished unique dye printed mug within 30min - 2 hour (depending on your current work load). If we did the same with perhaps slates, then they may take longer to sell so many, however the figures still conclude a huge profit on production cost. now if we only purchased 10 slates, the cost+shipping would of course be higher.. eg one slate $5 x10=$50+ shipping of $30 = $8 per slate (printed = $9 each) these retail at $20-40 each and only cost $90 to print these 10 slates, leaving a profit on production cost at $310.00 "Now why is shipping a huge concern to you?"
"phew" "did you manage to keep up with all that?"
get down to it. Your single mug (above) sold at 600% markup of production cost, and your slate at 300%. if you had always simply just doubled your production cost and sold at that price... how much money have you given away, and how much have to got left to grow your business venture? please note* all these figure will vary SLIGHLTY, with each setup, but in the end still produces a fantastic business opportunity!
Now of course, from this 600% profit we have not considered, nor taken account of items such as utilities - water and electric power and perhaps gas heating for room/building, computer time for you to create the artwork, insurance costs (medical and liability), telephone/internet cost (to obtain the order), transport cost to deliver (family vehicle, gas, insurance, tags maintenance etc), staff wages (yourself+1 because you want to... at some point be able to have to funds to hire part time help when really needed as you start to grow). Many don't bother taking into account any of these, since they may only be 'small'.
But if you are not collecting the money for this how then will you ever be able to afford to get liability insurance, or even to fix the family vehicle? these bills incurred whilst making your customers gifts, are obviously paid by you regardless, but paid monthly or yearly and not per one mug. so as we did early dividing the cost of a box of 36 mugs, we can do the same with these bills, by calculating what each bill costs per day. When starting out, and if you were to include these operating costs then you may have a mug that you need to sell at $150+ LOL ( just a figure from my head) this isn't going to happen! however if you also can sell a few shirts a day also....
"but i only do this a hobby" this is a expensive venture to do as 'a hobby'. a hobby that wont produce any profit, even working from home, and will take you from your family time. But this is where will all start from, and armed with a business plan and market research we can quickly get this off the ground level. Link: http://wholesale.laughingprofessor.net/calculator-wheel-profit-margins-file-download-svg-png-eps-zip-?search=calculator