It is guaranteed that Qatar will not be able to sell super expensive LNG to Europe, but imagine the size of the situation, if they agree to a deal, then they are going to make a lot more. Sure it will not be as profitable PER basis, but if we are looking at the totals then it's going to be something serious. Imagine selling 100 products to someone for 10 dollars each, that is 1k dollars, then imagine selling 1 million of the same thing for 1 dollars each, that is 1 million.
So the difference is staggering, and they could drop the price and remove the date stuff and they could make a ton of money that way as well. Doesn't mean they will, but they could if they reach an agreement.
This doesn't really calculate the limited amount into the play. Sure they could sell a ton to Europe and make more profit that way, but then what happens when the resources ends? They need a guaranteed situation so that they would not be left hanging when their resources ends, or when Europe finds a renewable alternative and leaves Qatar.
Qatar is already selling this for a lot more money and could continue to do that for decades and they are quite rich anyway, so they are not like paying some debt or poor nation hence they could continue to do this and would live fine. If they take on Europe, then they will be out of resources quicker, and will make more money for short span of time but less in the long term.