One Prioritization Technique That Actually Works

Before I explain how I prioritize, let's us have a look at what is commonly recommended:

1. The Boston Matrix. One of the most common bits of advice you find to help you prioritize is the Boston Consulting Group Matrix. This is a simple grid with urgent/not urgent on one side and important/not important on the other. All you need to do is put different tasks into the appropriate grid square and this will help you prioritize as you do urgent and important tasks first.
2. Adding effort. A variation adds a column for effort required and then you assess whether importance, urgency and effort is high, medium or low. Based on these evaluations you can choose your priorities.
3. Prioritizing by time required. This technique focuses on prioritizing through the time needed to complete the task. You list everything you need to do, give each item an estimated time then group the under 5 minutes tasks together and do those as one group. Then move on to the task that would take 15 minutes and then so on. In this way you can clear a lot of work easily. You can reverse the time order as well and do the tasks that will take the longest time first.
4. Rating by A, B, and C. A means is critical to the success of your job. B means not critical but needs to be done and C means not critical and doesn't need to be done. Give each task an A, B and C then start work on your As then your Bs etc.
5. Most important first. In this technique, you simply choose the most important task to do each morning and then do that first so at least if you do nothing else the most important task has been done.

I've tried all of these but none of the them has worked. Here's why:

1. Everything ends up being important. It is quite hard to decide if something is important or not. Also what you think is important is not always the same as what your boss or organization thinks is important. You end up giving everything importance. 
2. Everything is urgent. Other people regard their work as urgent even if you don't. Unless you are very senior, their sense of urgency wins.
3. Large amounts of reactive work. You get into the office and then there are a million different things that have to be done that aren't on your list or planned for.
4. Boss disagrees or changes their mind. Funny how yesterday's absolutely urgent is replaced by today's absolutely urgent!
5. Fast changing environment. It is hard to prioritize if things keep changing. 
6. Failing to update it. I have a burst of enthusiasm for a week and then fail to keep my grid updated and it becomes out of date and unusable.

So what works for me?

The only way I have managed to prioritize my work is by giving everything a cash value. Quite simply, every task I evaluate in terms of its contribution to the following cash measures:

1. Income. If I didn't do this task, how much income would be lost? If no income would be lost then it is not a priority. Income tasks are higher priority than all other tasks.
2. Expenditure. If I didn't do this task, how much would costs increase by or how many savings would be missed? Give an approximate cash value. If there is no impact on cost savings, then it is not a priority. After income tasks, expenditure tasks are the next priority.
3. Risk Management. From audit to risk analysis, there are some tasks that if not done would present a cost to the organization. These tasks need to be done but only after the income and expenditure ones unless there is a deadline or the risk cost is very high.

By thinking about all my tasks in this way, I can prioritize them in a way that makes sense to others including my boss. I can say, if I don't get this done today we could lose such and such a contract, giving the value. This protects your time and gives you a quantifiable way to assess your priorities. 

How do you prioritize?