I found some more information about Zip750 online. Also, more thoughts, because why not? I remember at the time thinking Zip750 drives and media looked very cool, like they would look good with the Power Macintosh G5 or a TiBook.
https://www.dpreview.com/articles/2389304106/iomega750mbzip(More or less, a press release.)
http://www.tomshardware.com/reviews/generation,567.html(Technical review)
The drives themselves were (All USD as of late 2002) $150 for an ATAPI internal, $180 for a USB 2.0/1.1 drive, and $200 for a Firewire drive.
The 750MB media, in an 8-pack, was $12.49/disk, so you're talking about $100 for a bulk pack of media. That's 6 gigs of total storage. 250 and 100 media was still on sale, for less, presumably for people keeping those drives.
The 750 drive could read and write 250 media and could read 100 media. I'm presuming Iomega's thought was if you were moving entirely to 750 cartridges, you'd just copy stuff onto your computer and then back onto new 750 media. If you weren't moving entirely to 750, you may have kept a 100 or a 250 drive available to write the 100 media.
The technical review indicates that performance was "okay". It was nowhere near Iomega's claim of 50x50x50x performance, relative to CD read/write speeds, but that it was
respectable nevertheless, especially for the convenience and durability you were getting.
Their final verdict was that Zip750 is overpriced, but I don't think in 2002 anybody was buying these to save money on anything. It was going to be purely for a better or more productive workflow.
There was backup, archiving, and syncing software included in the kit, I don't know how many people ended up using these tools. It could be useful if it helped you keep track of a particular piece of media that a particular file is on, but I'm imagining most people archiving stuff just wrote an approximation on the label
I'm guessing that anybody who could afford Zip750 probably also had a CD burner (unless they were upgrading an older computer, a laptop, an early iMac, etc) and at the time, the perceived infinite durability of writeable CD media, as well as the lower cost, would make that more suitable for archival. Certain software like Toast eventually gained the ability to create multi-disc archives, so you could put very large directory structures in place onto several CDs or DVDs. I don't know if Iomega's software did anything like that.
Sometimes I very briefly lament the death of small transportable cartridges. A similar-in-spirit system meant for backups called RDX exists, but that's really entire 2.5-inch SATA hard disks in ruggedized enclosures that plug into a special dock. On the other hand... a yearly subscription to a terabyte of data now costs less than just buying a 1TB USB external hard disk, which themselves are also very inexpensive.