Before the digital era, the top of the line film EOS camera was the EOS 1v. It was UAS$1899.
With the battery pack booster, the pricing was around $3000.
The EOS 1v was marketted as being waterproof.
The EOS 1v was released just over 11 years ago, in February 2000.
In 1998, Canon brought out the EOS 3 in 1998, for around $1400. Today it is $1699.
If you allow for a 3% price rise per year since 1998, that would end up at around $2055 (EOS 3) and $2788 (EOS 1v). If you want to argue that time should mean that things are cheaper, then...
So quite clearly, weather sealing does not mean a camera needs to cost > $3000.
But another way to look at this is that the difference in a digital camera that shoots 6fps at 22MP (5D3) and a film SLR that shoots 10fps (1v) is $1800.
How much of the $1699 is electronics for film that can be ripped out?
If the cost of that was ~$200, then the "digital" part of the 5D Mark III is worth $2000 out of the $3499 price tag.