This here is 160 pavers, 3.88 pounds each for 621 lbs total. Add 40 for the pallet and you get about 660 lbs on the forks.
It is about the maximum that I can put on a pallet and still lift it up from about 3ft high. That is, the empty pallet is put on top of a full pallet of pavers that is about three feet high, then loaded up with the 160 pavers. I can just barely lift it from that height.
Note that the center of gravity of the full pallet is nearly 2 ft forward of the fork frame. I am sure that another hundred pounds or so could be lifted if the pavers were stacked higher and closer to the fork frame.
I found that bringing the pavers in as shown in the picture is very convenient. I can reach most of them from a kneeling position without having to carry very many of them to where they need to be placed.