Okay, first let me state that I smoke... Just never indoors. I take it outside and have done so for 16 years or more.
With a few exceptions, everyone is missing the point here....
Even though I'm a smoker I would be very leery of a camera or lens that smelled of tobacco smoke for the same reasons I'd be concerned about one that smells of mold or mildew... It's the damage that's done over time as the smoke leaves a tar/nicotine coating on the internal mechanisms and electronics, optical surfaces, etc.
To illustrate what I mean, when I bought my house some years ago the previous owners had smoked in it. The entire house needed interior paint (although it had been repainted just a couple years before), but master bedroom was the worst. We ripped out the carpet (2-3 years old) and curtains and were able to remove the odor pretty easily... However the walls still dripped brown when we washed them with TSP. Even after several very thorough cleanings, it took 3 coats of special primer and two top coats of high quality paint to cover up the remaining tar & nicotine stains on the walls!
I saw this, too, when I sold homes. Smoking inside a home really puts people off, first because they find the odor objectionable but even more-so because it means a big cleanup will be needed to eradicate what's left behind even if the smell itself is gone. I'm sure it's just as bad with a car that's been smoked in for years. Cleaning the exposed surfaces only resolves part of the problem. There are still coatings inside ducts and behind the dash, inside door panels, etc., etc.
If anything, tobacco smoke residues are more insidious and harder to get rid of than kitchen grease, house fire smoke damage and certainly the occasional exposure to campfire smoke.
You can use all the remedies you want to remove the objectionable smell.... But that doesn't do anything to remove any residues that have settled on the inside of the camera or lens. You'd really have to do a complete teardown, very thorough cleaning of each part, then a proper reassembly of the item, to be certain.
Now, being that the OP's lens has only been in a smoking home for 6 months, there probably isn't significant build up or any real damage done. However, the buyer doesn't know that with any certainty... All they know is that the item came from a smoking home and that this the odor is a clue that it might have problems hidden inside.
So, really, the objectionable smell (to some... my brother in-law quit smoking 30+ years ago and still loves to get downwind of a smoker whenever he can) isn't so much of an issue in itself. That can be handled. It's more that the smell is a clue that there could well be deeper, hidden problems.