IMO, 1TB is completly reasonble. You can get ~10 GB of storage several places for free which covers most things and minmaxing 2-3$ per month is generally a waste of time.
Basically, there are only 3 Dropbox tiers: 0, 1TB, or infinity.
But the argument for dropbox is that you have a client for almost every platform you can use. With S3 you'll have to use a 3rd-party software, which might not function properly.
So really, most people are buying <30 GB of storage + a lot of bandwidth and a decent UI.
With that in mind the number of people with more than 1TB to store either need a streaming service or actually have original content which breaks their model.
Why do you consider Linux support worth $0 (since you want to switch from one $1.99/mo service to another) instead of a number between $24/year and $120/year?
For Dropbox, storage is the only source of income. Most of their income comes from people like me who are modest users ( < 100GB, not a lot of transfer).
Offering intermediate plans would make nearly all users high-loss users.
(I also can't understand why people are expecting to pay only $2 per month for 100GB of highly redundant storage with a top-notch client.)
Even going past the fact that OverGrive is $5, I won't support companies that think currency conversion is a way to leech more money from non-US customers. Yeah yeah taxes, but then the £ price should be around £27 and not £29. Its crystal clear what they're doing.
And Google is permitted to mine your Google Drive data for advertising purposes. You are just paying in a different way.
If that's acceptable to you, that is fine of course. But for me, data privacy is worth more than $2 or $3.
(No, I don't trust Dropbox either, but for different reasons.)