'The only thing eBay appears to have done to ameliorate it has been the introduction of "item specifics",'

Unfortunately it's the Item Specifics that can skew the results, in my experience.  I've posted about it several times before and yep, the Grand Canyon and other inland items are still appearing at the top of search results for "original watercolour painting seascape" when sorted by Price because the sellers have wrongly put "Seascape" in Item Specifics.