Old stocks are cleared by discount sales generally. Another way they clear it is buy two get one free scheme. They will sell a pack of three. 2 will be new stock and third one will be old stock. If all the three are from old stock the customer may not come back for next purchase.
All the expenses they are incurring will be added into the cost once regular market started. Last month I was travelling to New Delhi from Hyderabad airport. In the airport Sensodyne paste sample pack were being given to travelers. I got one. It is a fresh stock and quite good. After that I started using that paste.
So free samples are for sales promotion only.
Honesty is the best policy.