Incorporating in Hong Kong is actually far more expensive than incorporating in Mainland due to the yearly required accounting audit fee which starts at an absolute minimum of 15,000HKD a year  - if you really push for the best deal. On top of Address and standard operating costs you'll need to set aside 30-35k HKD a year. 

Note that companies incorporated in Hong Kong have limited access to Mainland China market, and we suggest you go directly for a 100% foreign owned company in Mainland China due to costs, market access and also you can make a work visa to mainland China with the company. We also offer full banking support and RMB -> Foreign currency transactions + conversions for foreign companies without the need for any local parties.

Typically Hong Kong Audits no matter how few transactions cost from 20,000HKD to 40,000HKD per year and upwards. There's no exception to this rule except if the company files for dormant status so be sure to get this included when you incorporate the company in advance.