Actually, the car analogy isn't far off the mark.
Your car's engine can deliver a certain amount of power, but if you tried using it at 100% load continuously, it'd probably last a few hours before it tore itself apart. Ever wonder why a soccer-mom SUV can have a 500hp engine, while an 18-wheeler makes do with about the same amount of power? The truck engine is rated for continuous load: it's five times as heavy and costs five times as much.
So it is with bandwidth: if you want a product that can deliver 50mbit in bursts, you'll get it for $40/month.
If you want something that will deliver 50mbit, guaranteed, continuously, you'll have to pay what that service actually costs.
That said, we know from Korea, Japan, Germany, etc that consumer-level connections can be far better than they are in the US, and for far less money.