For those looking to jump into the HE-400 pool, there's a vendor on Ebay selling them for $324.##, with free economy shipping in the U.S. If you desire 2-day FedEx shipping, then the charge is $24.##. Keep in mind, the HE-400 is being sold by a vendor who is not authorized. However, a SquareTrade warranty is offered for $49.99 and I believe it is for a 3-year term.
Additionally, though, if you buy a pair of HE-400s that are used, keep in mind that the warranty does not transfer from the original buyer to the future owner. So, finding a used pair on the forum could still put you in the same category as buying from a non-authorized vendor.
To me, though, the HE-400 is certainly one of the best bargains in headphones today. Sure, one can apply some sound adjustments to be able to have the headphones suit their tastes. Then again, I don't think there are too many of us who have purchased a pair of headphones that we've completely loved out of the box. Over time, we've realized that a certain signature wasn't for us, so we sold them and moved on. After having the experience to move up the HifiMan food chain a bit, I've realized that an upgrade from the HE-400 doesn't really necessarily mean that one would get an HE-400, and with much more of what the HE-400 offered. Instead, one is essentially getting a more refined sound. To lots of music genres, the ability to have the HE-500 or HE-5LE handle those, then those models might be something worth considering. However, I'd really encourage someone considering an upgrade to see if you can demo a pair that you're considering before taking the leap. Sure, there are vendors who offer a 30-day return policy, but personally, I try to avoid using that option if I can because I'd hate to abuse it in the event I really needed to use it.
In the end, I've realized I'm a tweaker. I'll always be a tweaker and having a bit of challenge to fine-tune the HE-400, for me, is well worth is because the HE-400 has quite a bit of grunt to it which can make much of our music sound quite stunning.