Ken,
You're looking at the same machine in 4 different levels of trim. They're all made in the same Chinese factory by the same workers from the same castings, the only difference is the level of quality control that the individual resellers are willing to pay for. Better QC equals better bearings, better motors, closer machining tolerances, etc., they all equate to higher price. Good book for any woodworker looking to buy power tools is "Poorly Made in China: An Insider's Account of the Chinese Production Game". While it doesn't deal with tools, it gives a a good look at the mind-set of the Chinese manufacturing industry in general.
Add in that only one of the versions you mentioned comes with the for-real Byrd Shelix head(there's a difference) and you'll see why I bought the Powermatic.
A note to Larry:
I know where you're coming from, I'm an OWWM member myself. I've traveled that path with 3 machines, one is in the shop, the other I could get to the point that I could sell it with a clear conscience and the last went to the recyclers at a tremendous loss. That one could be in the shop if I'd been willing to shell out $2K in machine shop time for a contractor saw. And I spent literally days spread out over months of what little spare time I have on these machines, time that could have been better spent building stuff.
Not all the members here have the mechanical ability or the time to spend restoring Old American Iron. I search Craigslist for "Powermatic" every morning, for every one of the 160's I've seen that look like the one you found on eBay, I've seen literally dozens that look like they were rode hard and put up wet or left outside in a leaky shed since Grandpa died 20 years ago. And all the sellers seem to think they're worth $1K+ just because they say Powermatic on the front and they're green. Here's an example from a local Craigslist broker:
Powermatic E16 16" Planer. Almost $2K for a planer that's been repainted and is in "good working condition" which means the motor runs and a board might come out of it smoother than it went in. No mention of whether it will come out parallel on both sides, torn out or with burn marks because the feed rollers are bent and won't feed at a constant speed. Or whether the bed has been dished by years of slamming boards through it at too deep a cut. Or any number of other things that could be wrong with the machine that would require expert inspection before purchase to find and machine shop time to correct after you brought it home. Add in another $600 for a Byrd head and it's easy to see why most folks want to buy new. It ain't easy being green.
Like I said, I bought the PM 15HH and haven't been disappointed. It's the wrong color, it was made across the world but it arrived in good shape and is working with minimal adjustment. And I have a 5-year warranty if it breaks.
My $.25 worth,
Bill