Della has somehow managed to scrimp together the tiny sum of one dollar and eighty-seven cents. It's taken her a lot of effort to put together such a small amount, but even so, it's still not enough to buy her husband, Jim, a Christmas present.
As we're told in the first paragraph, Della saved up the money through "bulldozing" the grover, the vegetable man, and the butcher. This means that when she goes out shopping she always drives a hard bargain, haggling whenever possible. By doing this, she's able to save a penny here and a penny there, but nothing really substantial.
Saving pennies like this is a pretty humiliating experience for Della. She's so embarrassed at having to haggle that her cheeks burn with shame as the various shopkeepers she encounters silently impute parsimony, or stinginess, to her. They don't have to come right out and tell her she's being stingy; their withering looks say it all.