LEDs are around 10x more efficient than incandescent bulbs. A 100W incandescent equivalent LED bulb typically consumes 10-12W. A 70W LED would put out as much light as 700W of incandescent.
Given idea just how much more light this is:
The designed lighting for a room in my house is 2 x 60-watt incandescent bulbs.
The equivalent wattage in 3 x 40-watt led bulbs is equal to 2 or 3 fluorescent light fixtures in an office building.
Traditional automotive headlamps are halogens and much more efficient than conventional incandescents. It was only in the last decade that LEDs beat halogens on lumens per watt.
I don't think there's a limit to how bright they can be. The law limits the lights to "70 watts", which I believe is intended to limit brightness but misses the mark. I bet the law was passed back when headlights were incandescent.