Penny wise and pound foolish
Careful with one's spending of small sums of money but careless and wasteful with larger amounts.
There isn't a great deal to be said about the expression 'penny wise and pound foolish' other than it is approximately 500 years old and originated in England. It is first recorded in Francis Meres' Luis de Granada's Sinners Guyde, translated, or as Meres puts it 'digested into English', in 1598:
Least he (as it is wont to be sayd) be penny wise and pound foolish, least he I say, gather ashes, and cast away flower.