$200k for 2.9 BTC at $69k.
Or buy the same amount a few months later for $48k.
Either way you have about 3 BTC.
You could still do the mortgage. 🤷♀️
Discussion
Or buy less a few months later for 100k. Plenty of pretty smart people thought that had a very good chance of happening. Nobody knows what a future exchange rate is going to be. This is wholly dependent on what your own reserve asset is, and how volatile you expect its future exchange rate to be.