"From my own experience and that of other trainees I know, we are paid about €10 an hour and charged out at about €200."
I don't have much familiarity with billing practices in large Dublin firms, but €200\hour for a trainee sounds outlandish. I rarely charge that myself. I would have thought that anything more than €70\hr would be very hard to defend until a trainee had at least a year under his\her belt.
To get the true cost of a trainee, you need to take the total cost over the training period and then look at the number of weeks they actually spend in the office. By this measure, a trainee is equivalent to pay of circa €26k per annum for the hours actually worked. A secretary in a rural firm could be on as little as €20k (though €26-30k is more normal) and a good secretary is undoubtedly more productive than a raw trainee.
Without a doubt, a good trainee can more than pay his\her way; but in a rural setting they are certainly not cheap labour .