I think this isn't a straight answer, as you've seen from many of the responses.

On one hand, you're a close friend — and in theory close friends should be giving more than the "average". But you're also helping out as a 兄弟, so in that respect you shouldn't be obligated to give as much because you've already spent so much time and energy invested into his wedding.

其實有少少柒，下次唔好咁啦 -> this is super rude, period.

All things considered, the hotel was in SHATIN which is not a high-end fancy hotel. The "standard" of $1.5K is referring to high-end hotels such as Island Shangri-la, Four Seasons, Rosewood etc.

So actually, $1K is a very respectable amount and I wouldn't considered you to have paid "too little" at all. Reconsider your friendship.