You can't say that Pete. If Shels had been playing Deportivo in the First round proper of the UEFA Cup, after being on a good run, I doubt they would've got much less of a crowd. Likewsie, ahd they drawn a nobody team form Eastern Europe instead of Deportivo, they would probably have struggled to fill Tolka, let alone get 22k out.
It's the calibre of the opposition that is the primary motivation to the Irish sporting public, not the competition. Asa secondary point - the size of available stadia is also a big crowd-limiter for Euro gamesoutside of Dublin. If Shels played Man United or Roma in the Inter-Toto Cup, let alone the UEFA Cup, they'd get more than 22,000 at it. If Cork played them, they'd be stuck with the Turners Cross capacity.
Irish people want to watch big-name glamour football teams on their doorstep. Hence, they turn out in their thousands to watch second string sides in meaningless friendlies. The context in which they see those teams is therefore secondary to actually seeing them at all. Throw in a competitive element in the form of a European tournament, and in particular an Irish opposition on a good roll, and they would flock to see any big team regardless of the tournament. 22,000 is not the high water mark for a European crowd in Ireland.