A few questions:

1) How do you know the new place can’t match the counter offer?

2) why do you think the folks who hired you for less than your current salary would not understand sticking at your current job for 25% more and a role change?

3) if you took the raise/counter and it wasn’t fulfilling would you be willing to take a job paying 30% less 1 year from now? Why or why not?

4) why did you want to work at the other company you just signed and offer letter for?

We’ve lost candidates after their current employer drastically increased their salary. It happens, normally before an offer letter is signed.