Here is some data for you from something I was doing earlier this year.

Cottered crank spindle - 7.6oz With the stock BB cups, bearings, etc. - 11.8oz

Stronglight 118mm spindle with bolts - 6.7oz. With Stronglight BB cups, bearings, etc. - 10.9oz.

Stock Aduprat Universel cottered crankset/chainrings with cotters (Beautiful by the way) - 38.2 oz.

Stronglight 93 crankset/chainrings - 21.9oz.

Stock Normandy 36H QR High Flange front hub (100mm spacing) - 5.6oz without the skewers.
Pelissier Professional 36H QR High Flange front hub (100mm spacing) - 5.5 oz without the skewers. Top of the line French.
The Pelissier is lighter despite having flanges that are 3mm larger in diameter.

The original Simplex Prestige derailleur must have bit the dust (as most do) so the bike had a Suntour Honor RD (mid level) on it. It weighs 12.9oz with the hanger. I am replacing it with a Suntour Vx that is 8.3oz.

Let's add that up. Stock parts 68.5oz, replacements 46.6oz if my math is correct.

We haven't even talked about the rear hub, freewheels, stems, seatposts, rims and tires.