The aforementioned Special Economic Zone (SEZ) Tourism Visa for Shenzhen is no longer HK $100. I went to two China Travel Service offices in HK (Kowloon and Wanchai) last month and inquired about this and both times was told the cost was HK $400. Even asked the concierge at the HK Intercontinental Hotel. He intially said HK $100 for US passport holders, but when he called someone to verify, he found out it had been raised to HK $400. Regular one time entry visa fee into China is HK $450 if applied for in Hong Kong at the China Travel Service offices. So you still save a little if you're just going to Shenzhen but not as much as before.