How can anyone guess how many slaves were used to build the pyramids when they have no idea exactly when they were built or what techniques were used?
There are records that give the approximate dates for almost all of the pyramids. Maybe not the day of the week, but within a few years.
Archaeologists have dug up the worker's communities around the pyramids. The analysis of those digs gives a pretty accurate estimate of the worker populations.
As to the techniques, there are as many plausible theories as there are archaeologists. Perhaps more than one engineering technique was used.
Ed
