I bought a Purple mattress a few years ago. It was debilitatingly uncomfortable. After three nights I gave up and called them for a return. Their customer service spent quite a long time trying to convince me to keep trying: their pitch/theory was that their mattress is so extremely comfortable and all other mattresses are so extremely uncomfortable that the body gets used to that discomfort and it will take a few weeks or more to switch over to accepting the comfort of Purple. After repeatedly saying no thank you and eventually having to explain to them quite bluntly that their theory was complete horseshit, they processed the return... the "return" was a Salvation Army truck, which, when it arrived, already had two brand new Casper mattresses in it. I asked the guys in the truck if this was normal and they said "yeah, we get at least 1-2 of these every day".

FWIW, I bought an IKEA foam mattress + memory foam topper for about 1/3rd of what the Purple cost and it's been very comfortable for a few years now.