I buy higher quality scopes for all my guns now...I'd say at least 50% of the cost of the gun or more. My main rifle I paid $320 for new in '87....and $350 for the scope thats on it now about 8yrs later.
Another good line that are not as well known are Sightron. Very nice scopes, and I actually have one of those on my mk. Most of my guns have Leupolds.