that is what an id90 is! But that does not include taxes which will add to the cost, so you end up paying 30% of full fare for a standby ticket, seems reasonable to me
Thats how Zfare came about.. back in the day if you wanted to fly HKG to NRT, then you had ID90 CX, ID90 JAL, ID90 Delta ect.. lts of cash outlay, and lots of refunds processed by the airlines.. no good for anyone.
Nobody took each others tickets (most didn't anyway, unless they were alliance/codeshare or some ****)
By zoning the fares, you can use 1 coupon for
any Z carrier in your agreement on any route.. Hell I've even used one to a different city in the same zone on a more relaxed North American carrier. Even CX will let you use a Z ticket to SFO or LAX or JFK / YYZ out of HKIA.
As they are all zone 7 cities out of HKG, they all have the same value. If they were ID90's they'd all have different costs, and that wouldn't be possible.
The $3500 ticket (I assume to Tokyo) in Business is a great deal, I've been used it myself. Be sure to sign up for a SKYTEAM FF'er account, the points add up fast, + upgrades, lounge access.
CX Z in Biz would still only run you less that 1/2 that wouldn't it, but not worth the hassle.