Statement #1: Sarah spends $50.00 per t-shirt.
This statement correctly interprets a part of the expression because in the expression \(50x + 30y\), the term \(50x\) indicates that Sarah pays $50 for each t-shirt (where \(x\) represents the number of t-shirts).
Therefore, the correct answer is:
Statement #1 correctly interprets a part of the expression.