I just spec'd out a 60x18x18 sump. In Acrylic, it was going to be over $500, so I just went and ordered 1/4" glass and made it myself for less than $200.
Acrylic is getting high...
See if you can find some cheap 125 to 180G tanks on CL, or the like. I recently saw an old tenecor 180 for like $100.