In Act II of Pygmalion, why does Doolittle want only five pounds instead of the ten he is offered?

You are right. If you
have a look at this section of Act II, Doolittle deliberately asks for the money for the purpose
of spending it all and having a grand time over the weekend. He is quite open about this, saying
to Higgins "Don't you be afraid that I'll save it and spare it and live idle on it."
He seems almost proud of the way that he promises that there "will not be a penny of it
left by Monday."...