Experienced shoppers will notice a sometimes discrete rubbing of money across merchandise by vendors just after a sale. This is money from their first sale of the day and it means good luck for the rest of their day. Be aware during opening hours that these merchants are eager for their first sale and may quickly reduce their price before you even counter offer. Don't exploit this and make tourists look greedy for a few cents. Just be aware of it and try not to engage the seller unless you really are interested in buying the item. It may look like superstition to you, but it's religion to them. You can tell if you're their first shopper by how attentive they are.