@Jo Yeah, just hit up aliexpress and it looks like high power transducers start at about $100. And the last time I looked at plastic welding kits they were in the several-hundred-dollar range. Since I was making a pool floaty I passed.

60 watt cleaner trandsucers were 12 bucks. I just have no idea if putting a tip on one of those would have enough oomph to handle light sheet plastics. Would be pretty cool if you could slap together a sub 50 buck station and make stuff out of milk jugs.