[jhg]

You can talk to a patent attorney and obtain a so-called "non-infringement opinion". Patents are frequently rejected at their first iteration as being too broad and then they are "tighten up" by their submitters by adding very specific, narrow clauses. Ultimately your goal is to identify one of such clauses and then work around it. If you are working with an attorney, they have an access to full patent history and this really helps with the clause examination.

The attorney fees are in the range of few thousand dollars.

HOWEVER - if you proceed as is and if it can be proven in court that you knew about the patent, you are effectively committing a "willful patent infringement". In many jurisdictions this automatically triple damages should you be sued for the infringement. Be very, very careful with it.