a beka a head (that is, half a shekel according to the shekel of the sanctuary), for each one who passed over to those who were numbered, from twenty years old and upward, for 603,550 men.If I've done all my math right, the current best guess on this amount of silver would be 138,313 troy ounces, or about 9500 lbs of silver. That would have a market value today of roughly $2.5M. And that's just the silver, it doesn't count the gold or bronze.
For a people who had just come out of Egypt, no land of their own, to spend that much on a place for God to worship says something. My church a couple years ago spent about the same amount on a new worship center, and it took years to raise the funds. While the Israelites did "plunder" the Egyptians before leaving, this is still a significant amount of wealth, and it's all for the purpose of glorifying God.