Edit values of a select list in a view
I suggest you create a custom module and in hook_form_alter according to your expose filter module form_id  get your form element,then you can change the value of your expose filter without change the value of them (as what you want)
something like below code can help you 

function yourmodule_form_alter(&amp;$form,$form_state,$form_id){
   if ($form_id == "your_views_exposeform") {
            // first try dpm($fom); to see what you have there
            foreach($form['expose_your_field']['und']['#options'] as &amp;$item){
            //  repalce label of select option items with what you want
            }
        }
        }