A good comparison would have been striping hard disks to compare against caching with EEPROMs. You'd have more capacity, a lot more, and wouldn't have a technology that dies after a certain amount of writes, which is dubious to use for something that's being used as a cache, and written on rather consistently.
Performance of Raid 0 would be higher than a single disk, and you'd be increasing performance without a loss in capacity (per dollar). Or, if you wanted the same capacity. you could get higher performance disks, and compare them that way.
If I want to spend an extra $100 to make my computer faster, will it? Duh, of course. That's all this article is saying. Is it the best way to spend that $100? Well, that much isn't clear at all. It wasn't compared with much of anything else. Two high capacity disks striped, and two higher performance disks (but lower capacity) striped, versus one disk and EEPROMs. All should be the same cost. It's more useful information. You'd have three fundamental choices - huge capacity, high "Winchester" performance, and low capacity with EEPROM caching. You could do a search on the capacity trade-offs pretty easily, but the performance difference between this caching and a high performance magnetic disk in RAID 0 is much less clear. Obviously, the hard disks would win a lot of tests, and could be a better buy for a lot of people.
It is worth looking at.