As others have said, the money fixation is quite a common occurrence. I suppose because it is about feeling secure, my husband was never fixated on money before dementia took hold.
We've also been through the stage where he has accused me of taking everything he owns and leaving him with nothing. It probably lasted a couple of years in its most repetitive phase.
Nowadays my husband seems more content in that respect. Occasionally he will worry that all his money has gone but, with great difficulty in getting sentences out now, we certainly don't get the constant repetition about it.
For a couple of years he carried around £40 in his wallet. It never got used but it seemed to be the magic amount to keep him happy. The money is still in his wallet but he leaves it on his bedside cabinet now, and although he still looks at it from time to time, it is growing less important to him.
These days he prefers just a coin purse with small change. I suppose seeing lots of coins helps him feel he has enough, but he rarely had more than £8 in it.
I am glad the money obsession has almost petered out.