Thanks for updating! I really appreciate it when someone comes back to verify results of advice, even if it was someone else's advice and even if it turned out not to work (lord knows most of us have plenty else to do besides help people who in theory could be our competitors, so at least revealing the results makes it feel worthwhile).
Now when you say that 2 items "did well" I assume you mean they sold and bid up to satisfying win amounts. -That's really the only thing that matters. A listing could get tons of views and watchers but if it doesn't get a bid or it closes with a disappointing bid, then the promotion might not have been a good investment. Granted it doesn't mean there wasn't a more-important reason why an auction could go poorly, as you know it could be that the photos weren't good, bidders didn't like the seller's shipping/returns policies, etc. and it could just be that the starting bid was too high. But the idea is that a well-chosen promotion strategy would override those issues, because the more people taking a look, the more likely at least one will pull the trigger and bid.
Right now I have that exact situation with a current auction, where all I hoped for was at least one bid, as I set the starting bid as high as I've gotten for this item before, so I know it's "worth" at least that much, but it's a reeeeally unique item (comic strips that were printed only in one Memphis newspaper). BUT comic strips are a reeeeeally saturated category, so the chances of someone stumbling on this would be very low without promotion, in fact I would suspect that most comic strip fanatics haven't even heard of this one. And lo and behold, I have a bidder! Now if he would get even one competitor that would take this from "satisfactory" to "WOO, it's on now!" ha.
The thing that is really great about PLE is that it is quite cheap, namely when compared to PLS (promotion for Buy It Now). I paid $1.99 to promote this auction, and that's already done, so whatever the winning bid is, I will get, minus the FVF. But if I had listed this as a BIN (for $135, same as the starting bid on this auction) and if I had promoted it at the suggested PLS ad rate of 4.6% ..... then I'd have $6.21 taken out of my revenue, plus FVF. And mind you, 4.6% is one of the lowest suggested ad rates I've seen in a long time; for most categories it is now 6, 7, 8 % (I think it's like 8.2% for vintage necklaces, just crazy).
But you get what I mean? It's cheap, ha. I think the highest PLE I was quoted was $4.49, can't remember what item that was but I paid the fee and didn't regret it in the end, because that item fetched about $80 more than my highest hopeful estimate, I was so happy. Now, I haven't figured what all goes into calculating the PLE cost -I'm sure item category is part of it, but I know that the auction duration is. The longer the auction, the higher the PLE cost, which makes sense because the item gets steady promotion every day to the end. And I know starting bid does NOT change it, doesn't seem to make a difference.
Anyway, sorry for the long reply, don't know how much of this you could have figured out already. As for which of your items to promote or not promote, it is so dependent on the unique qualities of YOUR inventory, and only you know what your own track history is with them, so you will develop good instincts for this, I'm sure. But just remember the surest bet is to promote items that are the most valuable/popular (individually) but fall within a category that is very saturated overall. Then your highly desirable item won't just be lost in a huge crowd of search results for the general category.
