Those are good points to consider.
Part of your profitability will come from your ability to do the same type of job quicker.
Maybe also think about the amount of inflation over the past 7 years to raise the price by that percentage.
In the USA you might want to add about 16%
Then if you feel the material will be used extensively for monetary gain by the buyer, you should get your little hunk of that with the buyout.
Calculate it a different way as well:
How many hours will you need to complete the image? Multiply by the hourly amount you charge for covering all you expenses and profit (a number you can calculate using the process laid out here: http://paulmirocha.com/recent_business.htm#business_planning) then multiply by 2 or 3 for a buy out.
If we are talking about major advertising uses, you might be looking at 5-10x instead.
Need to leave or subscribe to the Sciart-L listserv? Follow the instructions at