If you pay for a search engine, they will be tracking you a lot more.
I know that seems counter intuitive but they already are getting paid, by you. You just choose one that agrees not to track you and erases your data at the end of the session.
When you use the free ones they have a vested interest in sucking every bit of money they can out of selling their information on you to every buyer they can find.
If you can not tell what is being sold, you are the product.