I don't know where people get the idea that haggling is part of the culture. If you go to non tourist areas there is no haggling. When you are buying tourist trinkets or blankets of course there is haggling. They have raised the price and you think it is a bargain when it is reduced to the real price. Reminds me of when Tioga George had some fellow do some welding on his unit. He did a good job and I think the price was about 100 pesos or less. He offered 50! That is wrong! Go to central Guad. and walk the streets. Try haggling and they will be insulted. You might get a small discount. Clarlk is correct about tipping. Many of the waiters only get that 65 pesos a day and rely on tips for their income.
Moisheh