[5e] I have a question about the Dash action in 5e. I, and most of the people I play with, have used movements in 5e as if it were it's own type of action and have assumed using the Dash action to simply give you another "movement action". This never caused any issues but now I am playing a rogue and can use Cunning Action to dash as a Bonus Action.

However upon rereading the rules on page 192 of the PBH it says:

When you take the Dash action, you gain extra movement for the current turn. The increase equals your speed, after applying any modifiers. With a speed of 30 feet, for example, you can move up to 60 feet on your turn if you dash. Any increase or decrease to your speed changes this additional movement by the same amount. If your speed of 30 feet is reduced to 15 feet, for instance, you can move up to 30 feet this turn if you dash. (Emphasis added) Does this mean that instead of say 30 + 30(action Dash) + 30(bonus Dash) =90 my movement is 30 + 30(action Dash) + 60(bonus Dash) = 120?

And to get a little more cheesy, if my wizard friend casts Haste on me does my movement become 60(doubled from haste) + 60(action Dash) + 120(bonus Dash) + 240(Haste Dash) = 480 obviously I wouldn't blame a DM for not letting this happen, but is it how the rules work?