The primary point to be made here for the benefit of the majority of forum members is that sphericals are a high maintenance item, and not too many members regularly spend the hours under a car to constatntly inspect for maintenance. For the majority without extensive racing experience they will likely have no idea of the difference in handling characteristics as well so close will be the difference.
Add to that they are expensive to replace, transmit large amounts of NVH and can transmit impulse loads that can cause structural damage to the chassis and mounting points.
Now if you are in the business of selling these items and told a customer that they are fine in a road car and failed to disclose that damage could result due to dramatic differences in form and function, and damage resulted due to the increased impulse transmission, then you are liable for the damage. You have also committed an offence under the trade practices act as you have misled a customer. They can also be defected so again you have not detailed the consequences so are liable for the costs of labour to replace, a refund for the goods and the fine.
Some things to perhaps consider.
SK is doing the members a favour, not screwing others out of an income. Private sales of one off items - "caveat emptor". Multiple sales like a business - Trade Practices Act.