To update a total value stored in React state when a cell is edited in MUI X Data Grid, you need to:
Use the processRowUpdate prop to handle edits
Update your state with the new total
Solution Code
import { DataGrid } from '@mui/x-data-grid';
import { useState, useCallback } from 'react';
function EditableDataGrid() {
  const [rows, setRows] = useState([
    { id: 1, name: 'Item 1', price: 10 },
    { id: 2, name: 'Item 2', price: 20 },
    { id: 3, name: 'Item 3', price: 30 },
  ]);
  const [total, setTotal] = useState(60); 
  const calculateTotal = useCallback((rows) => {
    return rows.reduce((sum, row) => sum + row.price, 0);
  }, []);
  const processRowUpdate = useCallback((newRow, oldRow) => {
    const updatedRows = rows.map(row => 
      row.id === newRow.id ? newRow : row
    );
    const newTotal = calculateTotal(updatedRows);
    setRows(updatedRows);
    setTotal(newTotal);
    return newRow;
  }, [rows, calculateTotal]);
  const columns = [
    { field: 'name', headerName: 'Name', width: 150 },
    { 
      field: 'price', 
      headerName: 'Price', 
      width: 150,
      type: 'number',
      editable: true,
    },
  ];
  return (
    <div>
      <div style={{ height: 400, width: '100%' }}>
        <DataGrid
          rows={rows}
          columns={columns}
          processRowUpdate={processRowUpdate}
          experimentalFeatures={{ newEditingApi: true }}
        />
      </div>
      <div style={{ marginTop: 20 }}>
        <strong>Total:</strong> {total}
      </div>
    </div>
  );
}