So you build a road up to the enemy city before you take it? I used to love doing that in Civ 2 when you could still do road spam. It made for more creative games. IMO road maintenance is too high in Civ 5 to do that though.
Road maintenance is 1 gold per tile? So if I make 5 road tiles it is 5gpt for a few turns, then each worker can remove 1 road tile each turn. It's less if you have the Commerce SP 'Wagon trains' (which also give +2 gold for land trade routes to other civs). Commerce is a good way to support your army. I am not sure if the road is in enemy territory who pays the cost, I only know it was affordable and cheaper than buying extra units to replace casualties. I think this would work well with CKN. Note; I only do this where the terrain is a problem and remove the unnecessary roads afterwards.
So the cost isn't really that bad, especially in the middle game. You don't have to build a road all the way from your city, you can just focus on difficult terrain then rip up the roads you don't need afterwards. Compare the cost with supporting one extra unit and those maintenance cost are pretty light.
For example I recently had a game where I was attacking a US city flanked by a mountain range with jungle 2-3 tiles deep in front of it ...oh and they had already built the great wall. I used 2 workers to first build roads into the jungle, now here is where I noticed a strange exploit. When I got next to the city the garrison jumped out to capture them and of course my ranged units killed them and I re-captured with a pikeman (possible because of the roads). With roads and the jungle cleared the city got swarmed by my ranged and melee forces (the GW had really got me angry by this point) and fell quickly thereafter. It then became a new source of gold because I quickly built lots of trading posts and on to the next city.
But the worker bait exploit is a worry, my workers were there for good reason but I can see that some players could use this to destroy ranged garrisons. In game it seems the AI does this with it's non-combat units as well, that is why you may often see workers charging towards your cities. Human players don't fall for this trick though.
Alhambra - 14
Big Ben - 17 Going to vote this down as I often get commerce but don't even try to build this wonder
Borobudur -16
Brandenburg Gate-5
Broadway - 18
Chichen Itza - 25
Colossus - 24
Eiffel Tower - 27
Forbidden Palace- 28
Globe Theater - 14
Great Library - 12
Hagia Sophia- 14
Hanging Gardens- 25
Hubble Space Telescope- 25
Leaning Tower of Pisa- 30
Louvre- 21
Machu Picchu- 22
Neuschwanstein - 26
Notre Dame- 21
Oracle- 29
Petra-22
Porcelain Tower - 22
Prora- 23
Pyramids- 3 Workers that support the offense! (see above), I would miss this wonder the most. Also damn easy to get.
Sistine Chapel - 27
Statue Of Liberty- 25
Stonehenge- 18
Sydney Opera House - 10
Temple of Artemis - 17
Uffizi- 21