"NFW does it reduce the mass by half. The Delta V budget is many times 500 or 1,000 mph."

How much rocket fuel is used to get 50,000' or to get a velocity of 1000 mph? [you can pick whichever is less].

Or different question is at what point is the first stage and 0 stages dropped?
Keep in mind that most first stages have considerable more gross mass that the upper stages and payload, so if say 2/3rd of first stage is used up by 50,000' point or 1000 mph, it could amount to 1/2 the mass of the rocket. And in addition to this is that once 1/2 to 2/3rd of fuel of first stage spent, one is accelerating at a significantly faster rate [so that 3rd of fuel remaining in the stage will give more accelerate and therefore as much velocity as say, first 1/2 of fuel of the first stage did- and same is true of any of other rocket stages].

Btw, I said 5 miles a couple times in above post and I meant 10 miles [or about 50,000'].