No, I don't think of security as a 'product'. Also you may want to be more specific. The low hanging fruit is the people that put some sort of service on a network with the password 'admin', because it's "trusted". There's no world in which that is a cost saving behavior, it's just supreme laziness. Now if you get into embedded space, particularly with a lot of legacy design components, ok, that 'network' is going to be trusted. I'd eye things *very* skeptically if someone claims it must be a trusted network and at the same time it is an *IP* network. It's not impossible, but it's *highly* likely that the "must be a blindly trusted network" is lack of understanding, or laziness rather than a statement of feasibility or cost.
No, security is not *necessarily* the opposite of usability, the problem is that in a world where "security" guy is over here and the "get stuff done" person is over there, the security guy tends to mandate things without understanding getting stuff done and makes bad recommendations. Further, you have various vendors convincing people their "security" solution improves security, while it merely adds complexity, frustration, and in many times, vulnerability. Ironically enough, a lot of security "solutions" decrease overall security by any reasonable measure (e.g. a web proxy solution that forces a local certificate authority into all browsers to let it man in the middle, a security monitoring system that demands root/admin level access to *everything* and becomes a point of infiltration, etc). If a "security" product doesn't look like a pain in the ass, then unfortunately the business decision callers don't believe it's security.
However, in new deployments and if you demand it of new products, we can have credible security without a huge cost or pain in the ass. The specifics vary situation to situation, but nearly all IP connected strategies I've encountered that previously had "blind trust is just needed" had a credibly secure hardening strategy possible that was also transparent or nearly transparent to operators and users.
Again, some older networks it's not worth the cost to rip and replace, but everyone should be striving for "I don't automatically trust someone just because they could access this specified network" as they integrate new things.