If you want technological examples, say someone calls someone else irrational for basing their website off PHP instead of Ruby. Someone calls the printer industry irrational for making it cheaper to buy a new printer than to buy ink cartridges or that someone buys a new computer because their computer is infested with malware instead of re-installing Windows. You could say those are irrational choices, but the people who are making those choices probably have reasons for doing so which may make sense to them. The person with PHP may not know Ruby and would have to invest significant time in learning it. The printer companies bottom line will make their decision rational to many. The person buying a new computer may not have the skills to perform the task, the local computer shop wants hundreds of dollars to do the work & the computer is old.

So on the surface we say "that's irrational", but then later after learning more, maybe our opinion would change to "that's actually rational".

Also this does bring up the point that we often have to make a choice on what to do without the power of hindsight or with incomplete data. This can make our choices look irrational to those who are not in our shoes.