Moshe draws the Mishkan's root downward

עוד במד' משכר הסרסור נתוודע מה לקח.

Further, in the Midrash: from the broker's commission it becomes known what he took (sold).

The Sefas Emes cites a Midrash that uses the image of a sarsur (broker): just as you can deduce what a broker sold from the commission he was paid, so Moshe's "wage" reveals the magnitude of what he transmitted to Bnei Yisrael — namely the Torah and the Mishkan.

דכ' ועשו כו' ושכנתי בתוכם ככל א"א מראה אותך כו'.

As it is written, "And they shall make… and I will dwell among them," "according to all that I show you" (Shemos 25:8-9).

The verses command the building of the Mishkan so that Hashem will dwell among Bnei Yisrael, and instruct that it be made according to the pattern Hashem showed Moshe.

פי' ע"י שורש מרע"ה שהוא כלל הדעת של בנ"י וזכה לראות באספקלריא המאירה למעלה כל שורש המשכן.

The meaning is: through the root of Moshe Rabbeinu — who is the collective da'as (knowledge) of Bnei Yisrael, and who merited to see in the clear mirror (aspaklaria hame'irah) above the entire root of the Mishkan —

Moshe is the encompassing da'as of the whole nation. Because he alone gazed through the "clear lens" of prophecy and beheld the supernal root and blueprint of the Mishkan in the upper worlds,

עי"ז בכח בנ"י גם למטה לעשות כמו כן.

through this, Bnei Yisrael too were empowered to make it likewise below.

it was precisely Moshe's supernal vision that granted Bnei Yisrael the ability to construct a corresponding Mishkan here in the physical world.

ולהמשיך כח השורש למטה.

And to draw down the power of the root below.

Through Moshe, the spiritual potency of the Mishkan's heavenly root was channeled down into its earthly counterpart.

גם פי' הכתוב שאשכון בתוכם בכל המדרגות.

This is also the meaning of the verse, "that I will dwell among them" — on all levels.

"I will dwell among them" means that Hashem's Presence rests within Bnei Yisrael across every level of existence, from the highest root down to the physical.

אשר אני מראה אותך כו'.

"Which I show you…"

This indwelling on all levels corresponds to the complete pattern that Hashem showed Moshe — the full structure from its supernal source downward.

וכן מצאתי באוה"ח:

And so I found in the Ohr HaChaim.

The Sefas Emes notes that he found support for this interpretation in the Ohr HaChaim HaKadosh.

Summary: The Midrash's image of the broker's commission reveals the greatness of what Moshe transmitted. As the collective da'as of Bnei Yisrael, Moshe alone beheld the supernal root of the Mishkan through the clear mirror of prophecy, and through him that heavenly power was drawn down so that Bnei Yisrael could build its earthly counterpart. Thus "I will dwell among them" means Hashem's Presence rests within Klal Yisrael on every level, from the highest root to the physical — as the Ohr HaChaim likewise teaches.