As of 2019, there are not many places in Hong Kong offering Spray Tan services. In fact, I cannot think of any outside of Central, nor could I find any even after checking the first 5 pages of a google search. Thus, any spray tan in Hong Kong will probably require a trip to Central. Unless of course you find a mobile spray tan service provider. I recall a few individuals who started a service, however I’m not sure they’re still operating.
Prices in HK vary widely, and should NOT be relied upon as an indicator of quality. As services are mostly offered at beauty salons, prices vary based on general service offering. (Places offering high-end laser or other beauty services will generally charge higher prices.) Therapists, like all of us, have their bills to pay and are generally less willing to deliver low-commission spray tans when they could deliver high-commission facials instead. Fair enough.
Even more importantly than with indoor tanning, please seek friendly advice and online reviews before making any decisions.