... That’s....not generally how it works (except for tourists), but I suspect that you’re just having a bit of fun at my expense.
Of course that's how it works.
If you want to design a bespoke coat of arms, it costs €4,400 to get it granted.
Edit: apologies if I was a bit dismissive. Your posting history makes a bit more sense of the question.
Most Irish people don't really care about things like this. There's a 'family crest' for almost every surname, and they know about that and that's it.
For example, theres a 'Murphy' crest. You can buy keyrings with it. It used to be a nice wedding present that when 2 people got married you'd get a plaque with both family crests in it. That's about the extent of the use of them. People don't use headed paper, or wax seals with the crest.
People didn't get specific about having a special coat of arms for the descendants of John Murphy from Roscrea for example. It's not something that would have been done historically here, but was probably common in the UK for those with titles.
But, yes, by all means you can get a Coat of Arms for use by you and your descendants. Michael Flatley for example got one a few years ago - you'll easily find the artists details, etc. But it's be rare for Irish people to get one. Not completely uncommon for Americans with Irish roots to apply for one though.
Personally, I can think of much better ways to spend money than on something that'll die out after a generation or two.