If changing the product is evidence of competition, then Google Search and Android must have some, since they are continuously being worked on and new versions released.
Responding to a specific price point is the sign of competition, not general improvements in the product. AT&T built a gold-plated, state-of-the-art telephone network in the “Ma Bell” days, without facing competition. (And gave us the transistor and C and UNIX while they were at it. Google in many ways fits the same “benevolent monopoly” mold. I think it would be unwise to take antitrust action against Google for that reason.)