“Forty Silver Sockets were made under the twenty beams – two sockets under each beam – housing one of its protrusions – and two sockets under each beam – housing one of its protrusions.”

The sockets were smelted from the half-shekel which was donated – each Jew gave an equal amount (half a shekel.)

…Whereas the Mishkan and her vessels were constructed from the donations that were contributed, “Based on the generosity of each individual’s heart.”

The difference is:
The vessels (objects) in the Mishkan represent a person’s service to God in the soul abilities –
the curtains represent the encompassing abilities – desire and pleasure.

The beams represent the ten internal soul abilities of intellect and emotions (3,7 respectively.)
On the flip side, the sockets which were the lowest part of the Mishkan hint to the service of Kabbalas Oil, simple obedience to God.

This obedience depends not on one’s intellect nor emotions (nonetheless it is the founding principle for everything else – as the source of all Divine service, is simple obedience.)

As such, the donation of the sockets differed from the donations of the other objects in the Mishkan.

When it comes to internal work, there are differences between every Jew and every Jew operates based on his individual abilities and talents, as such, the donation of the objects of the Mishkan was based on each individuals heart – whereas the sockets which represent simple obedience – every Jew is equal.