I cannot say any more than this.
I can't go any further.
I can't do any more than this.
There is nothing else that I can do.
I can't do anything more than this in regards to that.
I cannot do anything else about that.
There is no longer anything that I can do for that.
I cannot afford such luxury.
I cannot afford such extravagance [luxury].
There's nothing I can do about this matter.
I can't do anymore than this.
I can't do anything except for around this much.
There is nothing I can do about that.
The only thing I can do is that.
There's nothing left that I can do anymore.