Depends on your target audience. I wouldn't want to compete with Amazon as a general proposition. But there may be some specific niche that isn't well served by Amazon. For example, there could be some piece of Tarsnap's infrastructure that is irritating/expensive to create but that other companies want to use.

Note, for example, that Dropbox gets "substantial economic value" from running their own hardware. [1] And Tarsnap is in the position to offer a backup-specific white label service that other entrepreneurs might rather pay to use than rebuild.

[1] http://www.wired.com/2016/03/epic-story-dropboxs-exodus-amaz...

Who said 30% interest rate? If banks are lending at 6%, than a 30% higher interest rate would be 7.8%.