Mat 13:23 But he that received seed into the good ground is he that hears the word, and understands [it]; which also bears fruit, and brings forth, some an hundredfold, some sixty, some thirty.

Most of the words in Greek here are very familiar. "Good ground" is kalos (beautiful) ge (earth). "Hears" is akouo, and is a symbol for the body. "Understands" is suniemi, a symbol for the mind. The cycle of the seed going into the ground, a symbol of the spirit going into caring, producing a tree and bearing fruit is Christ's symbolic description of his mission, where his body is the seed going into the heart of the earth producing a new faith and a new world order. However, what is most interesting here is that Christ may also be describing a field producing diminishing returns.

Alternative version: But spreading the seed on the beautiful earth is those hearing the word and understanding; those then bear fruit and produce truly a hundred then they [produce] sixty then they [produce] thirty.

"Bears fruit" is from karpophoreô, which means specifically "to bear fruit." It is also a metaphor in Greek, as in English, for virtue. It is the positive from of the term used in the previous verse, akarpos, which means barren.

"Brings forth" is from poieô , which means "to make," "to produce," "to bring into existence," and "to do." It is much more the economic sense of producing something valuable than most translations in the NT would indicates.

The last phrase following poieô is a bit vague. It is: hos (who, which, that) men (certainly) hekaton (a hundred) de (but-moreover, then-now-certainly ) hos (who, which, that) hexekonta (sixty) de (but-moreover, then-now-certainly) hos (who, which, that) triakonta (thirty). Some of the confusion here arises from the use of "de" which can be the conjunction meaning "but," "and," or "moreover." However, it could also be the particle, which means "now," "then," "certainly," and "at once." In the KJV, it is translated as the particle (as "also") and then ignored later in the verse.

Most translations interpret this last part as describing different people with different levels of productive skills. However, I think it describes how a field, if planted with the same seed, produces less and less over time. In other words, it describes the law of diminishing returns. While a new idea may be greatly productive at first, after awhile it produces less and less.