1. The most expensive seal is the one which doesn't work.
2. What is the cost of "quality"?
3. Do you always get what you "pay for"?
The above novel concepts are very thought provoking. I do not believe there is a simple answer. I will try with the following:
1. Number one is obvious. It doesn't matter how much money you saved--if the seal doesn't work, the money and time have become sunk costs.
2. The cost of quality is a "soft" cost. It is very difficult to determine the actual cost of quality because it is reflected in all areas of the company: Service Department, Purchasing Department, AP, AR, etc. etc. etc.
3. Sometimes you get what you "pay for". There is more than one engineering solution to a problem. Each solution will have an associated cost. I believe you start with the least expensive solution. You may be pleasantly surprised.