I have a Livestrong treadmill, those are discontinued now but I got it on crazy super clearance because they were discontinuing the brand due to the association. It is definitely a just-below-gym quality one, and the difference is HUGE. Get as good of one as you can afford, and watch for clearances like that.
I'd also rather spend $500 for a high-end lightly used one on Craigslist than $400 for one new, for what you can get for that price.
I want to say I paid around $775 all in, delivered, but it was around a $1800 treadmill.