I don't think you can put a yearly cost of 15k$, if they already think 25k$ is too much. In their eyes, for the first 3 years (standard license duration in my field...), the TCO will be 45k$+hardware, which is even more unacceptable.
For the "exclusive" license, it all depends if your source code is actually re-usable by a third party...
What you can probably do is come up with a two-fold contract: 15k$ for 100hrs at 150$/h If the software delivered can run on the low-end hardware, company will save $24k/year. Developper is then entitled to a yearly payment of 12k$ for the first 3 years....
It's a win-win situation: if you fail, you still get the 15k$ and they still have a solution. If you can make it, you win 15 +(123) and they save (123)