I've never been particularly interested in visiting either, but you ladies and gentlemen polled it into first place, so I decided to give it a go.
Flight with Jinair from Incheon to Hong Kong then the Turbojet ferry to Macau then flights back to Incheon came in at around US$300, and that included paying extra for inflight meals and spacious emergency exit seats (well worth doing on low cost airlines, imho.
Picked up 4500 HK dollars from the bank and got my train ticket to Seoul.
Chokdee wondered if that'd be enough money...
The arrival at Incheon (have to change trains in Seoul) only gave me about 30 minutes of wiggle room, but I reckon that with only hand baggage, as long as I check-in online then I'd be ok. So, the day before, I tried to check-in online - no dice...
Changed the train ticket and planned to stay in Seoul overnight. Around midnight, I headed to Seoul.
Decided to buy a nice pair of Nike Air Max for the trip - on sale, US$40.
Korail 1st class has a lot more room and some snacks for around $8 extra, so I usually do that.