Why not simulate that environment exactly?
For example, let's say you have a number of problems for them to solve during the interview process. Before you get to these problems, show the candidate something like the following:
Explain, as you did in your question, that the company loses thousands of dollars while depending solely on the candidate to solve the problems. Then start the timer BEFORE you give them the first problem, explaining as you do that while you take the time to understand these problems, the company will be losing money. Then hand them the problem, preferably on a piece of paper with no further explanation and sit back, observe, and answer questions for them as you deem appropriate.
When they are finished with the problem, click the "Problem Fixed" button and evaluate their solution to make sure it meets the requirements. If it does not, click the "10-Minute Penalty" button, which will figure in the time taken to evaluate whether the solution was correct as well as add 10 minutes to the dollars lost by the company, and have them continue working as the Dollars Lost continues accruing.
Repeat for the remaining problems, and feel free to be creative with additional penalties to make it more stressful, such as "It took you 10 minutes to get to a computer", or "Unfortunately, it turns out the problem you solved was not the critical one, and it took you 10 minutes to find out that this one is the real problem", etc.
At the end you will get a concrete number for total dollars lost, as well as the qualitative experience regarding how they perform under pressure.
Here's a fiddle that gives you a working example of the above simulation (and here's the editable link if you want to tweak it).