In the sense of finding a good bargain or trade:
"Getting that new laptop for $200 was a great deal."
In the sense of "more" in direct comparison:
"That laptop costs a great deal more than this one."
In the sense of "very much" or "a lot" in indirect comparison:
"I desperately needed a laptop, and it means a great deal to me that you gave one to me as a gift."
In the sense of a good hand in poker:
"You were dealt two kings and three aces? That's a great deal!"
(that last one was kind of a joke, but it still works)
It can be used more than one way.
1. That's a great deal of cocaine you have there. (meaning a large amount)
2. That's a great deal for all that cocaine. (meaning a good price or business arrangement).
- 1 - When bartering or bargaining (also called dealing), one sometimes has an advantage in the settlement. For instance, when buying paying a price that is very low for a product, or when selling receiving an offer considered more than expected. You have made "a great deal".
For instance, in the USA some merchants (most automobile sales companies, and some other companies) will negotiate the price, and it is possible each customer will pay something different. The merchants are called dealerships.
"I have made a great deal on this new motorcycle!"
- 2 - In card games, one person is designated to pass out the cards (the dealer). If a player receives a particularly good set of cards it can be a "good hand" or even "a great deal".
"Wow, that last hand was a great deal!"
- 3 - It is sometimes an expression used by people to mean 'much of' in a favorable situation, as in "I make a great deal of money" or "I have received a great deal of offers". I don't think this last expression is as common as it used to be.
It can be used in one of two ways. The first is in the economic sense, meaning like you got a good price for an item.
i.e. if you were to find a useful book at a store for $2, someone would say you got a great deal on that purchase.
The second meaning is used to measure quantity, usually of intangible things such as feelings and emotions.
i.e. you could say I have a great deal of confidence, or that I care a great deal about my sister.