HIFIMAN HE6se V2 Planar Magnetic Headphones – $298 | AliExpress Deals

This is a good price for the he6sev2, but this headphone comes with some major caveats. In my opinion, most people would be better off purchasing the hifiman edition xs instead.

A very powerful headphone amplifier is pretty much necessary to get decent sound out of the he6sev2. Hifiman recommends a minimum of 2 watts per channel into 50 ohms, and many people who own these headphones recommend up to 5 watts into 50 ohms, which is an absolutely ludicrous amount of power. If you don't already have a very powerful desktop amp, don't even think about buying these.

In addition to the standard hifiman longevity/quality control concerns, the he6sev2 is notorious for the membrane magnets getting "stuck". While this can sometimes be temporarily fixed by physically removing the membrane from the magnets (such as by blowing on it with sufficient force), it's a known recurring issue.
Build quality of the he6sev2 is relatively similar to hifiman's low end headphones, it uses the same standard cheap headband as even the $109 he400se. The he6sev2 is also exceptionally heavy, at 470g (16.58 oz), and is generally considered an extremely uncomfortable headphone without headband mods.

The sound quality of the he6sev2 is renowned for being exceptional at a price below $500 (assuming it's driven by a sufficiently powerful amp), so these compromises would be justified if there weren't any viable alternatives.
However, the newer hifiman edition xs: have sound quality in what's generally considered a relatively similar tier (anecdotally slightly worse compared to a properly driven he6sev2), are lighter at 405g (14.28 oz) and are generally considered more comfortable (especially if you have a large head), are incredibly easy to drive in comparison (a powerful headphone amp is not necessary, and can even be driven with a decent quality integrated amp or dongle), and are substantially cheaper ($269 new, $215 refurbished).

If you already have a sufficiently powerful amplifier, don't mind modding the headband for comfort, and prefer the sound signature of the he6sev2, this is a good deal. If you don't fit all those criteria, I'd recommend purchasing the edition xs instead.