AZ,
Was this point approved by the Roshei Hayeshiva? It seems overkill to me; you could simply take the second one off the list as soon as the first gets engaged. There’s really nothing preventing the parents from asking for their money back as soon as a shidduch seems serious (unless there’s a condition which I haven’t noticed publicized), so you’re kind of going with the honor system anyhow. You’ve publicly acknowledged the difficulty some might have coming up with such large sums and, to your great credit, reduced the amounts based on the feedback. This would be another way of making the program more attainable for some.