It's not at all unusual for manufacturers to start upping the price on less-common spares as vehicle age increases. There is one very simple reason behind this tactic, and it's used world-wide....if the price goes up, people stop buying. If people stop buying, they don't have to stock anywhere near as many. And since by far one of the largest costs a vehicle manufacturer incurs is spares warehousing and distribution, they are "letting" consumers find other, cheaper sources for some parts.

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Cheers,

Anthony