The cost to play at the arcade can be represented by the following piecewise equation:
\[ C(h) = \begin{cases} 15 & \text{if } 0 < h \leq 1 \ 15 + 5(h - 1) & \text{if } h > 1 \end{cases} \]
To calculate the cost for three hours of play, we use the second part of the equation since \( h = 3 \) is greater than \( 1 \):
\[ C(3) = 15 + 5(3 - 1) \] \[ C(3) = 15 + 5(2) \] \[ C(3) = 15 + 10 \] \[ C(3) = 25 \]
Thus, the cost to play for three hours is:
\[ \boxed{25.00} \]