The velocity boost for launching from nearer the equator is only part of the advantage. Another major factor is that many of the most expensive commercial paylo

The velocity boost for launching from nearer the equator is only part of the advantage. Another major factor is that many of the most expensive commercial payloads (such as major geosynchronous comsats) need to end up in equatorial orbits. The latitude of the launch site is also the minimum inclination of the initial orbit the launch vehicle can provide. At the equator you can launch into any orbital inclination. At the North Pole you can only launch into polar orbits. At 45 deg. latitude you can only launch into orbital inclinations of 45 to 90 deg. The higher the initial orbital inclination the more work you'll have to do (the more delta V you'll have to apply) in a plane change burn in order to get into an equatorial orbit.