Designjets are not the cheapest things to run but for non-specialist needs they are excellent tools.
For those who use project management software, you'll probably also find you like printing Gantt charts out on them; once you've done an A1 and stuck it on the wall, printing Gantts in A3 is just a drag, and the print is too small...
If you just need the odd big plan drawn, ask around your local copy shops, they may have a designjet or an architectural plan printer, and the latter is very cheap to have prints done on, a few bucks for A0; just turn up with a PDF of the right dimensions on a USB memory stick. The machines are hellishly expensive, which is why the designjet rules in this space, and has for over a decade.