Used jet-skis go for as cheap as $200 Newest most expensive Sea-Doo on the market today is $16,000
depends on the skis!
Top of the line skis for one week is around €100.
There's usually not much use for oil with skis. Modern skis are mainly plastic, and oil won't do much for them. Older wodden skis are/were traditionally treated with tar as a sort of base preparation to keep the snow from sticking to them.
They looked very much like the skis we use today.
A one week rental (6 days) is starting at € 60 for a pair of beginners skis and up to €120 for advanced skis.
Salomon makes ski bindings for oversized skis, driver skis, Z10 and Z12 skis, steel skis, Guardian skis, various variety of STH skis and non-STH skis.
You wax your skis so that you don't stumble on the snow and you just glide over it for a smooth ride! Also, waxing your skis enables you to ski faster and it protects the bases of your skis, which if damaged can cause a rougher ride and can make the skis harder to control (trust me, I had skis with damaged bases and once they were repaired they were SO much easier to control).
Not much, except the ski wax and the skis.
skis sold without bindings are flat skis
Because you need skis, ski poles, shoes and warm clothes. I just got new skating skis, and I got them for $800 (they were 30% off!). I also have classic skis for the same price, and two pairs of poles and shoes. Though, I go skiing on a pro basis. I think you can get all you need for about $200 if you don't care so much about the quality.
Cross country skis are are much wider, intended to reduce ground pressure. Downhill skis are narrower, to reduced resistance, and intended more for packed snow.