I don't quite understand the argument you're really making (a less polite way is to say that you sound unreasonably entitled). "Asus, Dell, and similar" aren't making SSDs. They're buying them. And yes, it is and remains a premium feature.
I can buy it through other supply channels but this small handful of companies are intentionally sitting in innovative new technology so they can sell you it at a massive markup in a limited range of their "premium" products.
For example, just look at the Chromebook. Clearly it is possible to supply at a reasonable price, but yet a MORE expensive, Dell, Asus, or similar wont.
Any eMMC devices I've used in the past have had pitiful throughput, low iops, and random stuttering. Barely good enough for something like a tablet. Not really for a general purpose computer. Now, I haven't seen any detailed benchmarks of disk IO on the ARM Chromebook. Maybe it's got some new advanced controller that's capable of decent performance. But I'd bet that it's still far behind a high quality SATA SSD controller. And that's going to cost real money, and won't be present in a $200 device.
It's one of the reasons I hope to expect the laptop take off.
They'd just order SSDs from the exact same manufacturers that they're buying HDDs from. They put them in the same holes and attach them to the same connectors and Windows detects them just the same.
So my normal workstation laptop has a simple flash cache double the entire size of the main storage in the Chromebook.
SSDs remain expensive. They are a premium because they simply aren't worth it to many users. I'd love to have boundless, super-performance SSDs in every device but that isn't reasonable.
Then either your market analysis is better than theirs and you need to convince them starting all the SSD laptops/desktops and scrap all other ones OR fund a laptop which is made just for you because if everybody doesn't want it then Dell and elk are not betting all their money on one horse. As parent commenter said they too buy them SSDs and an SSD makes a laptop costlier and a costlier laptop puts people off especially those who don't know what is XOR gate.
>>look at the Chromebook
When you buy something from Google it's not the end of story. You keep buying from Google. Just like Android which is actually free(OS I mean). But Dell? You bought a laptop, end of story - they will provide you support for an year and that is in laptop's price already. So, a Chromebook and a Dellbook are different in this way too.