In other words, the price that Apple BTO SSD while rather high, they at least are giving us highest calibre performance among comsumer available alternatives for pretty similar price (which cannot be said the same with RAM upgrades). The question is if the user really need the performance, and if so, it would cost the same if not more to achieve that via external alternatives.
Also, due to the relative difficulty of internal storage upgrades later yourself, it is generally best to choose more than what you need now.
I look at it not so much as needing the additional performance, but not having to deal with clunky and potentially temperamental external add-ons. So I always try to get as much as possible internally within budget.
This time I went with an internal 1 TB SSD. 512 didn't really help me because it didn't provide much advantage over 256 in a practical sense due to the size of my Photos library, etc. With either 256 or 512 GB, I'd have to move that folder off the internal drive, so I went 1 TB. I even considered 2 TB, but that was getting too costly, but in my case it was moot anyway because Apple doesn't allow us the 2 TB SSD unless you get the Radeon Pro 580.
When I thought about it though it wasn't actually THAT costly. An internal 2 TB SSD would cost another CAD$864 over the 1 TB SSD. Yeah, that's a lot of money, but a name brand USBC 1 TB SSD with 1/5th the performance costs about CAD$550-590 from a reputable store with a good return policy, so the price premium to get quintuple the speed and not have to deal with the issues associated with external drives was only about CAD$300, which is about US$230.
