Nick sold 55 - 6 = <<55-6=49>>49 bottles of soda in the morning.
They sold 55 + 49 = <<55+49=104>>104 bottles of soda altogether.
They earned a total of 104 x $.50 = $<<104*.50=52>>52 in the morning.
So, they earned $55 - $52 = $<<55-52=3>>3 more in the evening than in the morning.
#### 3