Apple used to have a limit of three devices for employees who were buying its products for friends and family, according to IntoMobile. However, this is changing, and Apple is not setting limits, but they say that this must be within reason.
IntoMobile posted an example of what is reasonable:
Use your discretion when determining “reasonable quantities” purchases for friends and family. There isn’t a specific number limit — it’s a judgment call. For example, buying iPod devices as gifts for your nieces and nephews at a 15 percent discount is fine.
Meanwhile, posting on Facebook asking your friends who wants one at 15 percent off isn’t considered reasonable.