But they're still heavy, relative to everyday items.
Dumb anecdote: I once made a comment to a co-worker about handling hay bales. When I pointed out that the ones I needed to move weighed around 1,600 lbs his amazement was palpable: "Seriously? Grass shouldn't weigh that much!"
Since we are doing math and all, area of Wales is 20,740 km^2 ^1, this gives average weight per m^2:
0.0000675024 kg / m^2 = 1400000 / 20740000000
Now then, per ^2 soil weights between 1200 and 1700 kg per cubic meter. Let's take upper estimate to account for constant rain and minor human infestation in Wales (weight of cubic meter of concrete is 2400 kg ^3).
This gives depth of Wales that equals to the pressure experienced by dmurray's chest of 0.0000000397 meters of ~40 nanometers. That is greater than feature size in modern CPU's...
Well, there you go folks, I dare say that is a more useless (and maybe more fun too?) comparison than comparing pressure with jumbo jets.