My product and knock offs question

Lipstickmogul

Say someone has put a similar product to my patented one on the market - with just one change or something similar but maybe different material, etc.  I see so many products come out and soon after, even when they are patented, one comes out that is just a little different and less expensive...how does this happen if there is a patent?
Thanks!
Robin 

patentandtrademark

their copying may be unintentional.  notify your patent lawyer.  sometimes, people steal your idea because they want to and it helps them make money.