Word for "add value to"

If I want to describe two financial investments that are mutually beneficial, that is, the first investment increases the value of the second, while the second increases the value of the first, what single word can I use in the phrase "reciprocating ______".

It would be the opposite of devaluation, I guess, but somehow no one ever got around to making "envaluation" a word. "Mutally beneficial" doesn't work because it's not specifically pecuniary.

Edit: It's to be used in a heading, so I'm hoping for an "action thing", or, as I just learned, a deverbal noun [Wikipedia]. Like the noun attack from the verb attack, except specifically and solely pecuniary.

Consider, appreciation [in value].

: an increase in the value of something

He bought the statue because he believed there would be an appreciation in its value.

Based on the history of the company, you can expect a significant appreciation in your investment over a number of years.

There's been no appreciation in the stock's value.

M-W Learner's Dictionary

Growth is a term that is frequently used to describe gains in the value of a financial asset. While it's not specifically "pecuniary" as you put it, it fits in the phrase you provided:

Reciprocating growth

Return, yield, and gain are similar alternatives that may work as well.