By Atika Shubert, CNN

(CNN) -- Matthias Katsch says he was 13 years old when a priest at his Jesuit school in Berlin first molested him. His grades suffered and the priest pushed him to have extra tutoring with his teaching colleague, another priest.

This man, Katsch says, stripped him naked in the school music room, bent him over the piano bench and beat him in a sadistic ritual that was repeated multiple times over the next year.

"I thought there might be more boys like me but I always thought I was the only one with a second abuser. It was a terrible shame for me," says Katsch, now 55 and a campaigner seeking justice for victims of abuse in the Catholic Church.

"But I was shocked to find out that I was not the only one. There were many victims that experienced exactly the same grooming. That's when I realized this was systematic."

In 2010, Katsch went public with his story, triggering an outpouring of testimony from dozens, then hundreds of other survivors.

On Tuesday, the German Bishops' Conference released the results of its own report into sexual abuse in the Catholic Church over the past seven decades.

The numbers are staggering: "at least" 3,677 people have been abused at the hands of more than 1,600 priests and other members of the clergy.

More than half the victims were under 14, as Katsch was at the time, and most of them were boys.

Speaking during the first day of the German Bishops' Conference in Fulda, central Germany, on Tuesday, Cardinal Reinhard Marx, its chairman, described the findings as "shameful."

"We are always shocked and deeply shaken that this happened inside our Church -- and is still possible today -- committed by priests and clergy, the people of God. Those who were given the task to watch over people. We must look at this again and again. We have addressed this before. But we must do more."

But Katsch is doubtful that this report truly reveals the full scale of the crimes committed. The report covers the "absolute bare minimum" of cases voluntarily reported by individual parishes, Katsch says, adding that he believes the real number of victims may be 10 times that many.

"For the survivors, the urgency is we want to know the truth now. We have waited for such a long time, we want it now," Katsch says.

He also believes the Church must address the issue of what the German Bishops' Conference calls "material benefits for recognition of suffering."

"The average payment to a survivor is 3,000 euros ($3,500). And yet the German Church is the richest Church in the world. It's ridiculous. And they know it."

While it is unclear exactly where the German Church ranks on the global Catholic rich list, it is undeniably extremely wealthy -- far more so than the Vatican.

Last year, Germany's Catholic Church raked in $7.5 billion thanks to its 19th-century "church tax" alone, and it's expected to surpass that number this year.

In 2016, the wealthiest dioceses of Paderborn, Munich and Cologne together declared more than $13 billion in assets, from real estate to stocks, far more than the Vatican's estimated $8 billion.

Germany isn't the only country to impose a church tax -- Austria, Denmark and Sweden do as well -- but it does charge the highest rate.

If you are a registered Catholic, 8% to 9% of your income goes to the Catholic Church, according to German law. The same applies to other denominations, including the Protestant Lutheran Church. In the last census, 30% of Germans were registered as Catholic -- that's nearly 24 million people, far more than any other faith or denomination.

The only way under the law to avoid the tax is by officially renouncing your faith, effectively barring you from receiving any religious service such as weddings or baptisms.

The German's Bishops' Conference estimates that only one-third of German Catholics actually pay the tax but that still accounts for more than 80% of the Church's vast income.

While the Church spends considerable sums on charitable endeavors -- from education to care for the elderly -- and, taken together with the Protestant Church, is the second largest employer in Germany after the government, a number of flagrant examples of overspending has shaken trust in the institution.

In 2014, Bishop Franz-Peter Tebartz-van Elst of Limburg was removed from his post after an inquiry revealed he had spent more than $40 million on a renovation of his official residence, complete with walk-in closets and designer bathtubs.

The scandal earned him the nickname "Bishop Bling Bling" and he was swiftly recalled to the Vatican by Pope Francis.

Since then, the German Bishops' Conference has made a concerted effort to increase transparency, publishing annual financial statements for each diocese. But that is not enough for some critics of the Church.

"It's not transparent whatsoever," says Christian Weisner, of the Catholic reform group "Wir sind Kirche" ("We are church").

"The church appears transparent because it publishes financial information online. But these figures are very general and vague. When you look closely, you can't see exactly how the money is spent."

CNN asked the German Bishops' Conference how it calculates how much an abuse survivor should receive in "recognition of suffering" and was referred to their website, which states that a victim of sexual abuse could receive "up to 5,000 euros" with exceptional arrangements for "particularly serious cases."

Katsch is frustrated by the amount and the unrepentant language used to describe the payments.

"The Church paid me a recognition fee of 5,000 euros ($5,900)," he says. "They don't call it compensation. And I don't call it compensation either."

For many survivors like Katsch, what matters most is discovering the truth. He says he received a "recognition" payment of 5,000 euros from the German Catholic Church only after one of his alleged attackers confessed to abusing multiple children.

"They call it a recognition fee? Well, thank you very much, but that's not what I want," Katsch says. "I want justice."