Or maybe it floats on ICE! The fish tank used to be frozen solid.
You are correct in the fact that most wireless routers don't transmit at their fully rated speed, especially if you are farther away from it. However, even the real-life speeds of 802.11g and 802.11n are faster than most people's internet connections.
You either have an incredibly fast internet connection at 70Mbps, or you are just transferring files locally on an internal network. Transferring files locally is where you do see big speed differences with network upgrades.
It would be like if someone had a 5.0 liter Mustang that had a fuel line that only let a few drops per minute through. They're not going to make it faster by putting a supercharger on the engine.
Bumping up your wifi to gigabit speeds won't do dick to help your crappy 1.5Mbps DSL.
That might redeem it just a microgram.