First, the $60 for new blades for that car does not surprise me. Most of the newer cars take a specialized blade that is not available at the box stores. And the prices for them are ridiculous.
Places like Jiffy Lube have quotas for their employees; that they are required to sell X amount of bulbs, wipers, etc. each month.
Damaging something to sell a product is not right but has been going on for a long time. When I worked at gas stations in the 60's, I was instructed on how to conceal a razor blade in the toe of my shoe so I could cut tire sidewalls. I did not stay at that place very long.
Good luck getting them to admit the damage.