1) Using current technology and taking into account theretical
limits,
what is the maximum payload that could be landed on the moon

Question: do you mean

a) "using rockets currently in production"; or
b) "using rocket technology that has been developed and flown, isn't
necessarily in production anymore"; or
c) "using various rocket components that have been developed and could
be cobbled together into a moon rocket"?

If the Apollo program's Saturn V is resurrected, then you could send a
lot more tonnage to the moon per launch than if you puttered around
with, say, an "off the shelf" Atlas V or Delta IV.

The payload capability of the Saturn V could be duplicated with tweaked
Russian Energia hardware (some resurrection needed), or a bundle of
Delta IV heavies (some development of existing hardware needed), or
some configurations of shuttle hardware (development of existing
hardware needed). Or you could take Saturn V hardware and build even
larger rockets - some proposed derivatives of Saturn hardware could put
about 500 tons into orbit and send over 200 tons to the moon.

and what would be the cost in doing so?

Depends on the rockets selected; how much development is needed; how
many rockets are built for the program; etc.

So, could you clarify a bit what you were looking for? Just entirely
real, existing rockets?

Mike Miller, Materials Engineer