Tomtom maps are pretty expensive too.
I've got a tomtom (or, more accurately, my girlfriend has one I gave to her...) and it's excellent, couldn't fault it. The traffic info was particularly good too, when we were using the free trial, but the subscription is steep for what you get.
I dunno what Garmin charge though.
A quick google reveals that Tomtom charge £50 a year for the traffic info, £30 for map updates. Their website is poor enough, IRC, the annual subscription was £80 a year.
It's probably the same price in euros for Ireland.