含金量 originally refers to the percentage of gold an object contains. It's now mainly figuratively used to refer to the inner quality or value of something (比喻事物所包含的实际价值). So here it is not about "more financially rewarding", but says it is of higher quality or inner value.
非常得高 is wrong. There are many regions where people don't distinguish 的地得 in their local dialects. That's why these three are often misused on the internet. But the current standard of their differentiation is still strict. However, in this very case, whether we should use 的 or 地 is still scholarly debated. One school think that after 状语 we should always use 地 (except some idiomatic usages like 真的). Another school agrees partially, namely that after 状语 if the head word is a verb, we should always use 地, but if the head word is adjective then 的 is possible, especially when the 状语 is a 程度副词, like 非常. A third school support the mixed usage of 的 and 地 in general.
That being said, wide usage of 的/地 is a recent phenomenon heavily influenced by European languages. Inherently in a lot of places the Chinese language doesn't need it. In formal or official documents, in these places de will not be used.
You are right that 非常高 is the most correct form. But if the author really wants to use a de, it should be 的/地. 得 is certainly wrong.