I'm assuming you have registered your copyright. If not, you should do so. Following are 3 methods to set a price. You need to fill in the right numbers (I guessed at them) and make the calculations, then the offer price should be set at the highest of the three numbers (the highest and best use of your work). Good luck.
Real estate appraisers uses 3 methods to fix a value on a property: Market Comparison (what other similar properties in the same locale have sold for recently), Potential Income (what you can make by renting out the property), and Replacement Value (cost to build a new copy minus the depreciation of the property due to previous use, like the age of the roof or condition of the floors).
Market Comparison - my son is a non-famous part time artist in California. He generally sells bigger pieces, $300-400 is not unusual. I have not read your books, but assuming they give you some celebrity then I'd double or triple his selling price. That puts your offer price at $600 to $1200.
Potential Income - Investors will require a Return On Investment (ROI). 25% per year is probably low, but gives a starting point. How many of your patterns can be sold per year, at what cost per copy? If you assume 12 copies per year at $10 per copy, that gives revenue of $120/year. If that revenue has to support the 25% ROI then the market value would be $120/25% = $480.
Replacement Value - You might think of depreciation as the loss of value because the artwork has been on the market for a while, so those most likely to pay for it already have done so. If it is new work, or has not been offered before, then depreciation does not apply. To produce something similar to your work will take some number of hours of a skillful artist. You would set an hourly rate and the number of hours to come up with a work-for-hire price. Work-for-hire means someone else pays you to do their work and as a result they own the copyright. If a skilled artist with some celebrity offers his services for $100 per hour, and the work requires 8 hours of effort, then the selling price might be set at $800.
I hope this makes sense.