They produce IP (researching and producing very clear instructions for fixes) and manage supply chain (trusted replacement parts & tools, worth more vs aliexpress equivalents because they endorse them).
The things they make money off are largely substitutable. Their value add (well deserved IMHO) is trust.
The network effect is also at play here. It's a community-oriented operation, in a sense it's similar to GitHub or Wikipedia - their repair guides are actually on an open wiki that everyone can edit, and users have contributed a lot of guide as well, and nearly everything is licensed under CC BY-NC-SA 3.0.
Don't underestimate the value of consistency. If I buy an iFixit toolkit I can be fairly confident that there won't be wobbly bits, oddly creaking plastic, the grip will be the same across the board and that the steel will be of reasonable quality.
They produce IP (researching and producing very clear instructions for fixes) and manage supply chain (trusted replacement parts & tools, worth more vs aliexpress equivalents because they endorse them).
The things they make money off are largely substitutable. Their value add (well deserved IMHO) is trust.