I honestly don't know what is it with these laptop manufacturers that refuse to offer the 16GB RAM upgrade option. Since the RAM is soldered on, it practically forces me to buy a Mac to get enough of it... and the actuall chips don't use more space.
Broadwell-U supports up to 2 channels with an 8GB DIMM per channel.[1] For configurations up to 8GB, you only need to run traces for one channel. Supporting 16GB requires more design work (need to run twice as many traces) and wastes logic board space on lower-RAM configs. Apparently, Lenovo decided the trade-off wasn't worth it.
Edit: If the 2015 X1 Carbon is dual-channel, I'm not sure why Lenovo would lack a 16GB option. I guess mounting twice as many RAM chips could hit space constraints.
Basically, the problem the vendor has when selling a product with a large appeal is that they want to sell it at the highest price the buyer will bear. If portion A of the buyers budgeted $100, and portion B of the buyers budgeted $150 for your gizmo, how do you price your gizmo to extract maximum value from the buyers from A and B? If you sell it for $150, A won't buy. If you sell for $100, you're missing out on $50 from B.
The solution is to make minor modifications to your product to sell the Basic version to A for $100, and the Premium version to B for $150. If you've done your manufacturing right, the cost of one over the other is minimal, and you're getting the maximum value from both portions of buyers-- I mean market segments. :)
And to expand on your your issue with the availability of 16GB models... you represent a small enough niche at this stage that it's not worth Lenovo's effort to design and source parts to accomodate your segment.
But I can't buy any small laptop / ultrabook from Lenovo (or most other manufacturers) with 16GB at all, no matter the money.
Calling it segmentation would make sense if I could actually give a boatload of money to buy something that includes it. Getting a huge W workstation really isn't an alternative.
My Lenovo S540 came with 16gb ram plus SSD and 1920 x 1080 resolution, it's pretty damn small (I've travelled Europe to the States several times with it in hand luggage easily).
Apple sells to it with the 13" MBP, which you can get with 16GB RAM as a BTO upgrade. I doubt that many people opt for it, but it's not a non-existent market.
I didn't explain my point very well. What I was trying to say was how can "laptop manufacturers that refuse to offer the 16GB RAM upgrade option" (as izacus put it) be considered market segmentation (as AceJohnny2 said in his reply to izacus). It's not a segment to those that don't sell anything to them, and because they don't sell to them, they have no (first-hand) data on how big that segment might be if they were to sell to it.
I refuse to buy any laptop with less than 16GB of RAM.
Spent almost 1 year searching for a laptop to buy. Had to buy a 14" ASUS-RoG G46VW[0] and replace the screen for a 1920x1080 one.
I bought a Lenovo W530 just so I could get enough ram. 16gb isn't enough for me (I run a lot of VMs and high memory applications), so I wanted a laptop with swappable memory. I now have 23gb of ram. I believe the system supports up to 36gb.
They use 'barebones' Clevo shells, which are then configured by different vendors.
I have a laptop based on W230SD and I'm very happy with it. It contains a proper i7, not the underpowered U model and also has a 3k screen, 2x mSATA slots and is easily upgradable in a 13.3" chassis.
Not may people realise just how underpowered the U processors are for any real CPU intensive work. 4xxxU i7 processors are on a par with 2xxxx mobile processors.
You sacrafice ultrabook thinness and some battery life, but the return is a very powerful, cheap, upgradable laptop.
You can select a 16Gb option for the X250. It does say "single SODIMM" though, which presumably means single channel memory => a very expensive SODIMM & sub-par performance compared to a dual channel equivalent.
What gives?!