Order of magnitude it's within range. A single wafer for something higher end is worth tens of thousands of dollars. So whatever that weighs. It's not much.
A 300mm wafer at 0.775mm thickness that weighs that much would be a density of 15g/cm³: midway between lead (11) and gold (19). Silicon is only 2.3g/cm³.
A 300mm wafer should be much closer to 100g than 1kg. Another page (on the same website!) says 125g, which is pretty dead-on 2.3g/cm³.