I agree that 18% more chance of selling an item if it has a subtitle is a very low percentage (for $2). To be honest, it seems barely more than arbitrary and there's nothing to indicate what 18 is a percentage of.

For example, if you had a sample of identical listings and ran a test, and the results were that the listings with subtitles sold 18% more than the listings without, then that could well be a significant thing. But that's not what the statistic infers.

So, what's the chance of selling something on eBay? As in, for as long as an item is listed, what's the chance of it being sold. If you start at 100%, then look at things that will diminish those chances (price, poor titles, bad photos, little or no description, demand or lack thereof, competition, unappealing TOS...and so on ). The same things can increase your chances in varying degrees, some your competition may have bad photos, TOS and feedback and so on, and all of this fluctuates between items, sellers, categories....even the mood of the searcher on the day, which is why I say a percentage of a chance is barely more than arbitrary.

But lets say you have a listing with a relatively decent position in best match, healthy competition but not flooded, and have used most things optimally, your listing - as one among 100 - still manages to stand a 10% chance of being chosen over the rest. An 18% increase on that 10% chance means for $2 you can increase your chances of a sale to 11.8%. A mathematically and financially unsound choice for many listings.

That being said, when I trialled it, the first listing I applied it to sold out in a week. I didn't have a huge amount of stock, admittedly, but there was a noticable increase in traffic and sales.

Personally, I wouldn't bother using them to give more information about the product, I used them to tell potential buyers why they should buy it from me.

What I mean is, if I'm going to pay $2 for an additional space, albeit small, I will use it to further define and advertise my presence on eBay in its entirety. Advertise a postage cap, same day shipping, a money-back guarantee, a warranty - something exclusive to your store or about your service, and something no one else is telling people at a glance. If people have searched for a product and found yours, they already know what they're looking for so product information is largely redundant unless it's something that genuinely acts as a selling point and won't fit in the main title (eg 100% Australian product). Again JMHO.

I'm not trying to sell subtitles to anyone, by the way, it's been months since I used one myself. :^O