Formatters are off-topic for this, styles come first, formatters are developed later.

My other reply:

How about this one? it more closely mirrors the switch example:

match suffix {
'G' | 'g' => mem -= 30,
'M' | 'm' => mem -= 20,
'K' | 'k' => mem -= 10,
_ => {},
}

How about this other one? it goes as far as cloning the switch example's indentation:

match suffix {
'G' | 'g' => {
  mem -= 30;
       }
'M' | 'm' => {
  mem -= 20;
       }
'K' | 'k' => {
  mem -= 10;
       }
_ => {},
}