I work in IT in Dublin. There is a growing IT sector, but the larger companies here are a lot of support and infrastructure (Goog Amz etc).

Not saying there aren't plenty IT jobs, but you can't look at size/investment alone without looking at what kind of roles are actually there.

I'd also note that while companies get plenty tax breaks, actual income-tax is pretty high. Accommodation is pretty pricey near the centre too, though not as bad as London.