Formula for a Payment Scale at Different Thresholds

I need a formula that will work for all occurrences in cell K5 in the attached. There is a grid as you can see to the left that has a different dollar amount paid once you hit certain thresholds. For example, if I have 5,000 total calls the first 3,734 will be paid at $37.50 per call, the next 726 calls will be paid at $39.14, the next 796 calls will be paid at $55.47 cents and so on. I want to be able to put any number of total calls in cell L4 so that L5 will give me the total dollars earned.

Anything after 6,339 will be paid at $55.

I added a column to calculate the differences between the price levels, which gets fed into the formula. One price level actually decreases in price, which may be a typo. If you change it, update the formula to contain the proper price difference.