It is looking like melamine is the most cost effective and least labor intensive route. I can use 3/4" plywood as a solid base for wheels and melamine for the rest of the shelves. The units will likely be 8' x 6' tall based on just getting 8' sheets of melamine. Lowes will cut it free is every cut is greater than 12" wide.
The melamine is actually cheaper than I thought.... $36 for a 48" x 96" sheet.