It is going to depend upon both lamp life and technology.
Generally the shorter the life, the higher the lumens per watt, and some high power Icans (the GE's with HIR) use a special IR reflective coating on the inside to further increase Lumens/watt (by reflecting IR energy back onto the filament instead of radiating it), but your typical 100 watt lamp runs anywhere from about 9 lumens per watt for a long life lamp to perhaps 15 for some halogen lamps with relatively short lives (a few hundred hours or less).
A 500 watt halogen should be good for about 20 lumens per watt, some may be good for a little more, depending upon life expectancy.