You're figuring just ticket sales.
Did you forget that to have four seats in the lower bowl of REA you have to join the Fighting Sioux club at the Coaches Club level ($1100 per year)?
Four in the lower at REA:
$1100 FSC membership
$345
$345
$345 * 2/3 (Coaches club discount)
$345 * 2/3 (Coaches club discount)
At that, the per seat price for over half the lower bowl jumps to $562.50.
You have to be a FSC member for most of the upper also, but not at the $1100 level, but there is no "club level" seat price discount up there either.
UND hockey is the UND Athletics cash-cow.
Alternatively, imagine trying to fund a football program with just one home gate.