Mattress industry actually seems to oddly be booming lately (in that they keep opening way more stores than seems to make sense everywhere). The thing is, mattresses are one of the most marked up items you can buy, so any sales they make are huge (and salesmen are paid on commission, so low costs for owners a lot of the time).
They’re a bit more like cars though. There really are differences between types and brands as to comfort and reliability and such, but to a large extent it’s really the same models recycled for a few years between real changes for any given brand (like how a 2016 [Make] [Line] is the same basic model as the 2015 and 2017 for a car, but in 2012 they had some major new release and in 2019 they’ll have one again). They are also like cars in that you should never pay the sticker price at a mattress store (salesmen have a decent bit of leeway to discount that mattress to make a sale since, as I said, they are hugely marked up). Certain mattresses are like an old Honda Civic too, in that they’ll last 50 years (not sure if that’s an exaggeration or too conservative right now for the specific ones I’m thinking of), while others will start loosing their luster in 5 years (though any decent mattress should last 10-20).
Source: Brother worked in the mattress industry for years. He hated it and got out, but he knew the stuff at least.