Competitive pay

This has happened to me.
When startups post job they write competitive pay in thier posting.

Then later after interview they off er you $20/Hr.! And thier excuse we are a start up so can't offer much.

Then why the hell did you just throw that word of competitive pay in job description. Just because Amazon and other companies have that in thier posting.??

Don't you feel that competitive pay is a misused term. Almost all job posting have this. I don't get it. What is the competing with ?? MC Donald's ?

P.S. I have 2 yrs experience and worked with a startup and a full time job. And I am not arrogant about it. But when you ask me to do something I am good at I demand a good price. I respect my work.