The difference is that we don't need a new GK because Polak is great keeper. Plus he's only 30. He can easily be our starter for next 5 years.
We're not missing out on him surely, and he's not free because we'd pay a lot for his wages.
Considering our team and so many holes that we have, it's jsut plain stupid to buy a goalkeeper at the moment. Use all the money at the disposal for a LB, new mid or two, possibly striker. Buying Donna makes literally zero sense because he'd upgrade us 0%.