I found one for $80 that I've been very tempted to purchase... but it would be the most I've spent on a single plant. Feel a little better knowing that price is typical
The prices difference between US and EU is nuts...
I paid €35 ($42.5) for a decent size plant and €50 ($61) for an alba seedling from a great breeding line.
Better make sure you get your gigantea from a reputable place. Due to their massive leaves, a healthy root system is even more important than "regular" Phal.