In a previous life I built a photo sharing community and it was quite common with >10MiB uploads, the limit I set was 25.
It’s just as you say, you want the highest possible quality (within reason) for rescale purposes (and 2x monitors like the iMac)
We're evaluating this product to replace our self-hosted "resize and deliver images on the Internet" solution and we definitely do have source images over 10mb. I'm not worried about the migration, but this means that going forward we might need our app (or worse our users) have to resize images down before uploading them to the image resizing service. That's a bummer.
EDIT: I just checked, 2.5% of source images are over 10mb.
An easy solution might be to have it accept an upload of a larger file, but automatically scale it down to fit under 10mb and then only store that as the new original.
I would've thought the workflow for these would be to upload a high quality source, and then the service creates lower quality/optimised variants.
I guess you have a limit as it is priced on total images stored and not storage/cpu used...