NumberFormat.getCurrencyInstance() from the chapter 27 (CodaPizza project)

Android Programming (5th Edition)
1

Hi all,
I have a question: why do we need use NumberFormat.getCurrencyInstance() ? In the book we set price of the pizza in this way:

 val currencyFormatter = remember { NumberFormat.getCurrencyInstance() }
        val price = currencyFormatter.format(pizza.price)
        Text(
            text = stringResource(R.string.place_order_button, price).toUpperCase(Locale.current)
        )

Isn’t easy just use “.toString” ? I mean this way:

Text(
            text = stringResource(R.string.place_order_button).toUpperCase(Locale.current) + "  "
                    + pizza.price.toString()
        )

thank you