I'm thinking of getting the 2TB upgrade too. It's a shame you can only do this with the high-end model.
B&H takes taxes now, at least for WA residents.I figure that if you have a computer that lasts 4 years, the cost of all of this per month isn't all that much. Check out B&H or Adorama or ..... you might be able to get your machine with no sales tax and free shipping .... that saves around $300.
I bought it because my budget was around $4000 and I also get the EDU discount. 1TB was just a little too tight considering my 2012 rMBP was 512GB and I was always running out of space, and that’s with me keeping my Lightroom catalog on an external SSD and using iCloud Photos. I don’t like managing a lot of drives and wanted to have a 500GB Bootcamp partition for games. Though today I saw the Samsung T5 2TB SSD on sale for $329 on Amazon and if I had known they were getting that cheap (I have one for Lightroom) I might have gotten the 1TB instead and a couple of those. Oh well. My internal drive is like 6 times faster.