10,000 values means shipping 10,000 values via HTTP to the browser - with the browser allocating memory for 10,000 HTML elements, and then creating a 10,000 value GDI (Graphic Device Interface) listbox which requires even more memory on the browser platform.
Abusing client resources. Why?
A DDL with 10,000 values? You must really dislike your users If I ever have more than 'a few' (domain specific as to what 'few' actually is!) items I switch to a Popup LOV, although the standard one in APEX isn't great it at least works. I still wouldn't want to try to display that many entries though.
Instead of the popup LOV I use modal LOV, it lets them search... as soon as they start typing a popup shows up, with them being able to keep typing and values get restricted to the desired filter...