James - Most Frozen Four venues are sold out, often well ahead of time. Exceptions were last year (80-90% full and a few years ago when they tried Ford Field in Detroit (indoor football stadium in a ghost-town). They normally play in an NHL rink with 18-20,000 capacity.
They've kept the price at about $200 for a few years, just this year raising the cost of lower bowl tickets about $30 (15%) for the set of 3 games.
Perhaps you are thinking of the NCAA Regional site games? They are often sparsely attended.