This article is from the Macintosh system software FAQ, by Elliotte Harold email@example.com with numerous contributions by others.
Apple rationalized its decision to begin charging for system
software by claiming that most people had been unable to get system
software updates from online sources or authorized dealers (and of
course they rationalized their refusal to authorize low-price mail
order dealers by claiming that Macs require dealer support) and by
claiming that charging for system software will make retailers more
willing to stock Apple system software and thus make it easier to
obtain. This denies the reality that System 7.0 was in fact readily
available from the primary sources of payware Mac software as well
as being freely available online. And I doubt a full-page ad for
System 7.0 in the software catalogs costs Apple any more than an ad
for System 7.5. This rationalization also ignores how previously
in large organizations only one person needed to be able to get
the system software from a dealer, online, or bundled with a
new CPU before others could freely and legally copy it. So,
despite Apple's protests to the contrary, it is now harder to
get a current copy of the system software thus creating a FAQ
where there was none before.
The easiest way to get System 7.5 is to visit your local
software retailer and buy it for about $99 (though I've seen
it as low as $90 and as high as $129 so shop around). You can
also order it from all the usual mail-order houses like Mac Zone.
It comes in two versions, one on high density floppy disks and one
on CD-ROM that also includes a couple of Peirce Printing Tools
extensions for QuickDraw GX. Both of these versions include
an upgrade manual.