使用具有HAVING原因和CASE-Postgres的GROUP BY进行求和

I've managed to find a very manual work around but I'm sure there is a much simpler method to what I'm hoping to achieve. Essentially I'm trying to get find out how many redempetions there are for customers who have achieved 'points' (sales vs their multiplier) and reached a threshold (2000) as one number Example table:I've managed to find a very manual work around