There are a number of variables which go into this sort of calculation. There is no doubt that attorneys make a fair bit of profit in these class action suits. But you must also realize that there is a lot of work and risk that goes into a class action. First, a law firm will be tied up, entirely, for months at minimum, and often more reasonably for years. And we're not talking a single attorney in most cases. We're talking about a partner or two, a few associate attorneys, all of their legal secretaries, and supporting staff. This is not to even mention the consultants and others needed to get the suit even off the ground in court. This is a huge amount of salary to keep up.
Next you have other costs such as filing fees, notification to the affected parties, copying fees (this is no small amount per month), research costs, and validation costs. All of this adds up quickly. Trust me the list goes on and on.
Now for the kicker. There is no promise or guarantee that the suit will win. Most class actions don't. So the attorneys of record for the plaintiff side take on all of the liability of these costs, for however long as the suit is in process. This is a huge level of business risk, spanning sometimes many years. Imagine an investor taking on this level of risk in a technical company? They will want a substantial reward at the end. Thus, the level of fees associated.
Remember also that of the plaintiff loses, they often have to pay the defendant legal fees, which are also sizable. This is a huge risk.
Finally, it's unfortunate that they didn't email you back promptly. But remember, in a class action you are not really their client. You are their means to an end. It's a rough relationship.