Those costs are relatively minimal, courts do charge fees (though I don't know how well that covers the court's expenses), and few class action suits go to trial - they are settled or dismissed beforehand.

Personally, I had to spend almost a week sitting in a jury pool at the courthouse. I lost about $1k in pay which was rather significant for me at the time. The lawyers did end up settling out of court though, and made $xx millions. So I guess it was all worth it in the end...