Your question is a bit like asking "how much does a house cost?" It depends.
There is a lot of work involved.
First there would be the investigation -- you have to find who may have taken it and then have some basis for alleging he did take it. If you can do the detective work yourself the cost is low; if a lawyer does it -- and fees range from $100 to $500 per hour the cost necessarily is high.
Second, you have to have a legal theory. I don't know the facts but copyright, trade secret, abuse of a license, patents, all may be a basis for suit and they each have their own peculiarities and needs. A lawyer would have to evaluate it for you.
Then there is preparing the papers and filing suit.
AND THEN MAJOR COSTS BEGIN. Will the other side say "Uncle" and if so what will they agree to do? Stop? That an pay you something? Pay you what you think you are entitled to?
Or will they fight and try to do a scorched earth defense and tie you up for years. If someone at Microsoft did it, imagine what they could throw at you while YOUR legal bills mount.
My advice is consult a lawyer and spend the few hundred dollars for a consultation and see if it makes sense to go forward.
