Actual sales figures are not made available to the general public. However from all reports and from what I've been told Fox has sold a LOT of Chan product. In fact, Vol 1 was their best selling classic film DVD set last year. Vol 3 has had strong pre-order sales as well.
The Fox exec who once said he'd lose his shirt on these releases probably could buy a whole new wardrobe (and then some) with what they've made on these.