Been watching this for a few days, was sitting on $449, which I already thought was a great deal and went very close to buying, today it's down to $364. Then on top of that there's the $100 Philips Father's Day cash back promotion. We have Prime but I think there's a free delivery within 4-5 days for non-Prime or $5.99 (or free with a Prime trial) expedited. I think there's 7% from cash rewards too.
The link above seems to bring up a third party seller initially that is slightly cheaper at $358. That one has a longer delivery time-frame and I don't know how much shipping is. But from there, you can access the Amazon-sold one.
These have great reviews and highly rated by Choice.
How does this compare to the xiaomi 3H? Cost to performance ratio and filter replacement cost