Yes, some sellers do well with this. I don't think you have to be a "mega seller" to do well with this. But the very first thing to ask yourself is: How beneficial will it be for me to have the top spot on the Search Results page?
For example, I sell single quantity, used/vintage, lower dollar, long tail items---generally not a lot of them listed, and generally not a high demand item. If a buyer conducts a fairly narrow search, my item will likely show up on the first page of search results, and, due to condition variations, etc, buyers are likely to look beyond the top item. So, for me, I see no reason to use PL Advanced. I simply don't need that top slot.
I don't know what sort of stuff you sell, but from the sound of it, you've tried this, and even though presumably you got the top spot in some cases, getting the top spot did not yield enough sales dollar volume to make it worthwhile. It's possible that you would have had similar sales result even if you were lower on the page. I suspect you are either paying too much per click , or you are paying for items that don't require the top spot.
But yes, some sellers are doing very well with this. But it definitely isn't for everyone.
