Why does the Torah repeat the weight of the individual Kelim?
Rashi: To teach us that the weight was in Shiklei ha'Kodesh, 1 which it did not mention earlier.
Which is double the equivalent Chulin weight.
Why does the Torah see fit to state the weight of each Kli, and the total weight of all the Kelim together?
Rashi: To teach us the degree of accuracy of the weight of the Kelim - there was no discrepancy between the sum of the individual weights, and when they weighed them all together.
QUESTIONS ON RASHI
Rashi writes that the sum of the individual weights was the same as and when they weighed them all together. If this was a miracle, what was the reason for it? If it is not a miracle, why does the Torah teach it?
Ramban (2, citing the Sifri), Moshav Zekeinim (84): They took a weight [of silver or gold], made a formless coin, and made Kelim from it, and they weight did not decrease. 1 They did not do so with them 2 (weigh before and after), rather, [had they done so, it would have been the same, for] the gold was [smelted many times and] was greatly refined.
Normally, one who gives to Hekdesh weighs on a balance scale with a Hechra (he gives extra, to make the Hekdesh go down and the weight go up). The total excess is greater if one weighs part at a time than if he weighs all at once. 3 Perhaps here they weighed precisely, without Hechra, due to the intents mentioned above (refer to 7:13:5:1-3, 7:13:6:1-5. - PF)
This Chidush applies even if they did not weigh all the Kelim together! Perhaps they weighed only before making each Kli, and at the end, all the Kelim together. (PF)
Newer printings of the Ramban say 'v'Lo Na'aseh Bahen Nes' (no miracle was done with them). Moshav Zekeinim cites the Ramban like an early printing 'v'Lo she'Na'aseh Bahem Kach.' (PF)