there should not be any duties on an import of a 35mm film camera to the US, unless the seller uses the incorrect harmonized code, or describes it incorrectly (and doesn't use a code. Without a code, it's up to the customs people to determine how it is coded and whether duties will be collected.)
tell the seller to use 9006.51.00, ‘used 35mm film camera’
I did this with an M5 just last month, zero duties...I've bought many cameras from overseas over the past few years, never any duty.
The tariff mentioned above only applies to lenses, not bodies. it's a different code: 9002.11.90. Don't use that one!
Further, have it sent via Express Mail (EMS) (i.e., the post office), not Fedex/UPS, if you can. The commercial carriers will sometimes charge a brokerage fee; the post will not.
My guess is the $40 you were quoted is actually a brokerage fee, payable to the shipping company.
Of course you may prefer Fedex/UPS for somewhat faster delivery, and that may be worth $40 to you...