I think this is expected. It's either increase price or cut costs, and cutting costs is easier for them.
I've always felt these delivery services would have it very difficult in Hong Kong. Everything is so close and convenient and many places already have their own delivery. I know some companies and mostly expats use it, but for about $20 each time... how much would they make? I hardly know of any locals using it, and for me, i'd rather go downstairs and buy something rather than waiting 45 min and paying extra for delivery.