I have driven a car where the steering wheel center was slightly off-center when the wheels were straight. No problem at all. As the problem was slight, nobody complained about it in mandatory yearly inspection. I drove the car 40 000 km like that. No accidents at speed whatsoever.
If you had a 4-wheel alignment done, this was probably caused by the alignment so it's their job to fix it. But otherwise I wouldn't care about the problem.
If I were buying a used car that has this problem, I would carefully check the wear pattern of the tires. If the date code on the tires is old, and no unusual wear has occurred (and the car hasn't been in an accident), I would say to the seller that it's very suspicious that the steering wheel is off-center and that it could be the sign of an improperly done alignment, so the problem of steering wheel being off-center needs to be fixed and the alignment needs to be checked. So, I would negotiate the price way down. If the seller agrees to sell the car for reduced price, I would drive away smiling, fully well knowing that I got a good deal, and not do anything to the problem of steering wheel being off-center.