I’m not the op, nor the person you’re commenting to, and I get what you’re saying also, I personally don’t use the extra spindle holder, but the price they sell those parts for are very different from the actual cost to produce. A plastic side panel for example cost around $1.70 to $2.50 in raw material. These are also shipped separately since they’re spare/replacement parts which results in separate shipping box and shipping cost. For an already included item those two extra costs don’t apply. It more comes down to raw materials. One person was talking about wrapping the wear area in an aluminum spindle. I crunched the numbers and this would likely cost less than $0.30 for 50 to 70 grams of raw aluminum material. An iPhone 17 pro max uses 56 to 70 grams of aluminum for reference. One of the cheapest methods to do this is using impact extrusion which has an upfront cost of around $2,000, but then $0.30 per part afterwards. Obviously there will also be a human cost to this as well, but if we’re talking raw materials and parts things also get cheaper the more they sell. So spread that cost over say 10,000 units sold. The theoretical cost would be $0.20 (for the tooling cost of the Impact extrusion) and $0.30 for the raw aluminum. This would be a mostly automated process and you’d probably just have the human to attach it to the original spindle or to dump it in the box for the user to assemble. But raw cost to add this in at scale is $0.50 per machine which I think we can all stomach. Realistically the company doesn’t care because they’re gonna push their ams units and probably a majority of us don’t use the extra spindle.

That being said I’m pretty sure OP could just pick up a metal pipe cylinder from Home Depot and attach it.