Precious rubber cup parts

Ordered brake rubber cup parts arrived from Tokyo for my VW Super Beetle 1302 costing 5,292 yen including Tax. Judging from ordinary common sense for these parts, ten times price, however they are unlikely as 45 years production air-cooled Beetle, how come?
I must inquire the rusting phenomena on the brake cylinder inside wall first, though I didn't neglect to change brake fluid every 3 years, occasionally, honing procedure must be done if the wall might have substantial oxidized deficiency.
Considering conscientiously, the cylinder inner surfaces should be processed by means of Chrome plating technology in to like a mirror, don't you think?
Because I touched everything, imagined I some fine omission work before I begin to change rubber cups into new ones.
In order to  prevent brake fluid leaking, I do insert a DIY 1 mm thickness round rubber pert between the rubber cup and the bottom of a sliding pusher part, counter-measuring 2-step stance.
Let's see what will happen, reporting later.