When it says "10000+ matched" that means that the search stopped after the first 10000 matched items. This means that the sorted results won't be an exact snapshot of all items.
If you want to see the most expensive items listed you should use the "Buyout Price" filter with some large value then sort.
Here's an example: https://www.pathofexile.com/trade/search/Heist/MdLLKyFJ