Not etirely correct. The change in pressure is largely due to the change in volume. The change in temperature is an adverse effect of this change in volume since the gas needs to exert work to expand, also known as the Joule Thompson Effect

Backpressure is actually reduced when you expand a gas into a larger space, think about it...would you rather blow through a drinking straw or a 3" pipe?

Temperature does not define the size of pipe used to transport gases, the limit is actually when the gas moves into critical (or choked) flow where the velocity of the gas becomes the speed of sound and the flow rate becomes independant of downstream pressure. A gas is a compressible fluid so is very felxible about the space it can fit in!

Economics come into play WAY before this critical point though, especially in a chemical plant. For choosing a pipe diameter in the processing industry we choose the optimum based on price to manufacture a pipe diameter versus acceptable system pressure loss from friction. We are also bound by acceptable velocities to ensure the pipe is not eroded.