Dropbox sells communication and peace of mind, which they believe to be worth $10. The amount of storage synced isn't really the product. Think about it like this: what if, rather than promising 1TB, Dropbox promised to sync "all your files"? Would you find that a more attractive offer?

I think the reason is similar to why Apple is offering 16 and 64 GB smartphone tiers, but not 32 GB.

I think this is more reasonable than you might think.

It might seem like 32GB is a good baseline, but I am using 3.1 GB on my 4 year old smartphone and 16GB is probably plenty for the vast majority of people. But, if your actually recording video etc then 32GB is not that useful.

32GB flash drives are like 8$. So, Apple saves a few dollars on millions of phones and people who think they might actually needs extra storage get a significant amount.

Interesting Apple do have a 50gb storage tier for iCloud for 79p/mo.

huh. that's new. but they have 16, 64, and 128.