The armor costs were determined by Heike, my boss, so I cannot speak to
her reasons for pricing them the way she did (I fully agree with and support that pricing though, and I can discuss my reasons). I think that it is also important to point out that neither Heike nor myself were involved in the creation of RMSS/FRP, so it is also quite likely that we have different ideas about the "rules of thumb" than they did.
Onwards........
Personally, I don't think that they are too high. I do think that some of the costs for other skills are too high, and I do think that doubling the DPs (from RM2 to RMSS) when the number of skills was increased 3x or more a more problematic issue at the very least.
By having the costs as they are does have the benefit of freeing up DPs to be spent elsewhere.