And actually, we crossed the 300 MB mark. My node (configured up to 600 MB) is currently at 490 MB usage.
Do different nodes use different memory formats? The stat sites I've checked, like Johoe's or BTC.com, peaked at just approximately 180MB.
The node memory usage is larger than the raw transactions size due to some bookkeeping overhead. The sites report raw size while nodes have real usage limits. 300 MB standard limit is the real one, including the overhead and it has been crossed already, though it is slowly trending down (445 MB right now for my node).