I too am in business spanning Singapore and Down Under (not in photog business). I understand your point even more as I tend to come across clients like you mentioned ealier in the thread. Singapore Clients or Singaporeans for that matter tends to make comparison with other vendors and would squeeze more deliverable out from you at a fixed price or suggest a price cut at every opportunity. Which client wouldn't try their luck?
Westerners tend to respect the contract more and would not indulge in that uncivilised manner.
Speaking in a fairer tone, all(I mean all) my clients have increased their budget without me even asking when they needed more photographs to be submitted. This is the first but I'm damn sure it won't be the last Think I just got lucky all these while.