Mavic spares come from europe and they sell them by the packet not individually (enough for one side normally), they may only fit one year of a certain model. So it wasn’t unreasonable, but they probably should have let you know before ordering.
Mavic wheels are nice but specs change too often and spares are Mavic specific for my liking. Also alloy spokes and nipples are more prone to breaking or seizing. Personally I like “standard” wheels with J-bend DT spokes and hubs with easy to get hold of spares.
If you have the time it’s worth learning to do your own repairs, it’s really satisfying and saves a lot of money. I taught myself when I had a crap bike that kept on breaking and no money to take it to a shop, I didn’t have a choice then 🙂