I think it is worth the cash, if strength is your concern, making a box that is 2 x 4 is a lot more rigid than a single 4 x 8 sheet flapping around. resistance to moisture is the biggest thing, honestly Id still use pvc even if it was heavy as melamine based on that alone. I used to be in the "just keep moisture out away and it will be fine". but after accidental dings and drops the wood gets exposed, swells, cracks the laminate, then your pretty much screwed and modifying the rack to get your gap back. Then after I moved, it pretty much destroyed my racks/cages as they get banged around so much. (perhaps your friends will be nicer than mine) didn't take long after we got in the new home before I noticed swelling and cracks.

Price used to be the thing that kept me away from pvc as cheapest I could find 1/2 pvc was $125 back when melamine was $27. Now melamine is $35 and I can get home depot pvc for $57. Even at $78 I think it is worth it.