Covering popcorn ceiling

We have a 1950's home with old popcorn ceiling. We have had a plasterer out to quote on either: Removal and replacement, repair, or cover up. We have opted for a cover up but have been quoted $5000 (AUD) for this to occur. This seems mighty steep, but with the shortage of skilled trades, we are having trouble even finding people to come and give quotes. My partner and I are checking whether it is viable to put a plywood ceiling (from our local hardware shop) up ourselves. I spoke to the plasterer initially about this option but he warned against it. In order to save nearly $4000, is hanging the plywood ceiling directly over the existing popcorn ceiling viable?