This can be as much work as creating the marquetry itself. There are lots of formulas that allow you to come up with an asking price, but these are aimed at the professional who is doing this for a living. One such formula takes what you expect to get paid per year divided by the number of hours you plan to work minus vacation time. This is your hourly rate. Next, figure your cost of materials for each piece including any waste. To this add your projected overhead rate (yearly expenses of doing business such as machine purchases, tools and supplies divided by yearly hours worked). With these factors you can come up with an actual cost outlay. Now you must figure in a profit. It is generally calculated at 30%-50%. So multiply your cost by 1.3-1.5 and then you have a selling price. The one problem here is if the piece is sold in a gallery their commission will cost you your profit so you end up working for an hourly wage only.
I have personally avoided the above by selling my marquetry outright and let the buyer add his profit after I’ve left the building. To expediate the pricing of my marquetry, I have simplified it by multiplying the number of square inches by a factor of 1-3 depending on the complexity of the marquetry. For instance, an 8” X 12” picture with moderate detail might be sold for $144.00 (8 X 12=96 X 1.5 = 144). Another example could be a box 5” X 6” X 4” tall with marquetry on 4 sides and the top. 2 sides 5” X 4”= 40, 2 sides 6” X 4”=48 and a top 5” X 6”=30 adding up to 118. Because of the construction of the box, I would use a factor of 3 resulting in a price of $354.00. This system is very flexible with no effort made in keeping track of time or expenses. It has served me well. I have looked for a better system, but to date have not found one.