Here's a funny thing: Amazon Fire Stick 4K *I'm getting one this x-mas just for testing.
This thing $35.00 gadget is advertised as "Dolby Atmos" ready -- even if it becomes obsolete in a few years, at least it's costs peanuts to replace. Complete opposite to those gigantic processors/receivers you actually have to plug them into -- not to mention all the speakers you have to figure out a way place properly in the room.
I'm honestly confused what this has to do with anything? Decoding Atmos on a chip isn't expensive, the whole point of Atmos is to distribute audio in a format that better scales between both stereo soundbars at the low end, all the way up to pretty literally as many channels as you can afford. Older audio formats couldn't do that.
Once you start adding niche, weird requirements like balanced outs, good room correction, a large number of output channels, etc is when the price starts going up, because not that many people are buying products for those features.
E: I should add, most good, current TVs decode Atmos and output 5.1 to optical out anyways if that's all you want. You don't even need any other device.