I didn't say you shouldn't charge them for cleaning, my point was you shouldn't refuse the job based on smoke damage. If it is beyond repair you try to sell them a new computer. Considering how much competition there is in this area it is silly to refuse perfectly good work.
Just the way I see it.
The problem is that some computers are beyond repair when there is tabacco smoke involved. It rusts the parts.
Just imagine (extreme example but so you understand) I have bought a computer from you with a 5 year warranty. Since I am a bad customer, I burn tabacco or/and other material near the fans before the 5 year is up (year 4 and 8 months). You get the computer and you smell the smoking material and the tabacoo but since you cover it, you would have to replace all parts that have been damaged by the smoke. It is the same thing as spilling water on it: External factors caused by you that damage computer parts.
Are you a smoker compl3x?