It must be harder. If it wasn’t, you’d be able to get to arbitrary pressures with a constant force. So, in the extreme, if you can get the air to 15 psi with yo

It must be harder. If it wasn’t, you’d be able to get to arbitrary pressures with a constant force. So, in the extreme, if you can get the air to 15 psi with your lungs, you’d be able to get the air to 1000 psi with your lungs, too. Another way to see that is to consider two tanks at different pressures that are connected to each other, and ask yourself why air will flow from the higher pressure one to the lower pressure one.