If you are capable of designing a clone, then you are also capable of designing a more appropriate board for your requirements and therefore make it cheaper.
Thanks for the advice guys, but I want to get a more objective answer: what price is more realistic for this board to make it more affordable and which modules the comunity consider redundant and they could be removed and what should be added. Is it possible to make a questionnaire for comunity and how to do it?
To get more objective answers, you need to ask more objective question. What is the purpose and target audience of your intended board? Is it a development board or end user product? If it's a development board, with what will it differ from the many other development boards?
As for ST development boards' a legal status, read it there: