There's two types of user here that go hand-in-hand:
The publisher, who cannot / will not create an API from their spreadsheets, but would like to (either to ease their own pain, or because their end users are asking for it, or because they don't want to share their entire dataset so often).
The consumer, who wants to access a little bit of their publisher's data without having to import spreadsheets en-masse regularly.
The publisher is the customer of the service ultimately, but the consumer will quite likely be the one driving the publisher to adopt it. Being self-critical, I'd say this makes it a bit of a tough sell (you're one step removed from the actual customer).
The publisher, who cannot / will not create an API from their spreadsheets, but would like to (either to ease their own pain, or because their end users are asking for it, or because they don't want to share their entire dataset so often).
The consumer, who wants to access a little bit of their publisher's data without having to import spreadsheets en-masse regularly.
The publisher is the customer of the service ultimately, but the consumer will quite likely be the one driving the publisher to adopt it. Being self-critical, I'd say this makes it a bit of a tough sell (you're one step removed from the actual customer).