Different "Asc" and "Desc" labels for different Views exposed sort fields
There's a feature for this in using the Better Exposed Filters module through certain combinations of BEF settings:


Set "Display exposed sort options as" to anything except Toggle links, which seems to give strange results
Under "Advanced sort options", tick "Combine sort order with sort by"
Save, and see what strings it outputs by default for the labels. For example:


  
  Price Highest
  Price Lowest
  Date listed Highest
  Date listed Lowest
  



Copy these into the "Rewrite the text displayed" field, then for each one put a | then the intended label, for example:



.

Price Highest|Price - Highest
Price Lowest|Price - Lowest
Date listed Highest|Date - Newest
Date listed Lowest|Date - Oldest


It then outputs as intended


  
  Price - Highest
  Price - Lowest
  Date - Newest
  Date - Oldest