I bought from HK a few times a long time ago but have found much better sources since then.  Never spend more than you are willing to flush down the toilet when you deal with them.  I would never consider buying large items(planes , etc..) or big ticket items(engines, etc..) from them as they have NO service after the sale. Their own brand of servos are in part re-badged Power HD servos.
As far as selling brand name items at HK  I know they get around distributor agreements and will buy from an unscrupulous overseas distributor ,sell it below what most US/Europe based dealers can sell it for and undercut them. They only buy enough product to skirt the law or where it costs more for the manufacturer to prosecute.
I would look for a US based company and try and buy product from them. There are some chicom items that only HK seems to carry but for the most part what they sell can be found elsewhere.