About the Aeropress, I guess the question is: When I press it down (in my case, using the elbow for added pressure) how many bars can a typical user reach?
Let's do a little calculation. For an upper bound, let's say you press your full weight onto it and the coffee grounds' resistance is not the limiting factor. That's maybe 90kg, times the acceleration of gravity, for about 900 newtons. That force is applied to a pi*(30mm)^2 or ~3^-3 m^2 area. That gives us a pressure of 900/3e-3 = 3e5 Pa or 3 bars.
James Hoffmann answered this with a modded aeropress with a pressure sensor: a typical aeropress brew is in the range of half a bar. The max he could achieve was 1.5 bars, but like he says, no one brews like that. He also found anything past 0.5 bars began to taste awful.
