What Drew said. 11x14 Portra 160 or E100G is now $31.50 per sheet, special order only, minimum order something north of $15,000. You can wait to participate in one of Keith Canham's special-order co-ops, but you'll still face the very stiff per-sheet cost. If you need commercial processing, you'll be up around $50 total cost per exposure.
Also, if you're looking to make big enlargements, depending on the nature of your subjects, the DOF and diffraction issues that make 4x5 vs 8x10 often a close call may become even more problematic.