There is (was?) a A380 flight with Emirates from Dubai via Bangkok to Hong Kong, and back, and you could buy tix for that last segment BKK–HKG for about 200 USD, or 300 USD business, or 400 USD first.
Cheapest way to get a shower at 35k feet (without miles wizardry), I’d think! (And who doesn’t want to shower on a 2 hour flight... :-)
If you buy a First-class ticket, don't just enjoy the parts of the flight itself, but also the optimizations around it. With my first-class flight from Dubai to Munich it was impressively efficient:
I got picked up at my Hotel in Dubai, in a car with WiFi where I could have worked, until the Driver dropped me at the first-class gate. No queues, friendly staff, dropped my luggage and went through security within 5 minutes of leaving the car. Went straight to the lounge, where I got drinks and could have worked some more, until I got picked up for boarding. First class is the last to board, to minimize waiting time in the airplane. Same idea goes on arrival: First class leaves first. I got straight to passport control before the 500 people from the lower deck were able to form a queue there. When I was done, my luggage was already waiting for me, picked it up and met my driver to get me home - again all within probably 5 minutes of leaving the plane. This first class flight really was designed to enable the traveler to be most efficient with their time.
That the luggage was ready was most impressive to me. At least Emirates marked the luggage, and probably loaded it in a way that first&business luggage gets out first, and fast.
Cheapest way to get a shower at 35k feet (without miles wizardry), I’d think! (And who doesn’t want to shower on a 2 hour flight... :-)