Hey Martin,
If I told you "its hard to say", it wouldn't be of much help. So let me take a minute or two, as this concern needs to be looked at from several angles of measure.
A healthy adult male panther can easily average 4-12 crickets daily, or the equivelent, with very large panthers being near the high end, smaller somewhat less. A healthy adult female more like 2-5. Since you will not likely see your chameleon actually consume 90% of what it eats, unless you sit by its cage all day, you will need a different approach other than counting what it eats. It helps to have a cage which minimizes or eliminates cricket escape. In this way, you can observe a reduction in the number of live crickets in the cage, either cup-fed or free-ranging. In either case, you would only want to present (or make available) a number of crickets equivelent to the high ends mentioned above on a daily basis. Each day, attempt to ascertain the approximate number of uneaten crickets remaining, and fill back to the high-end level. Whether cup-fed or free-ranging, a quantity of the cup-fed crickets will become free-ranging by escape. It is important to have some good food available for the crickets to munch on as they await being munched on. We rate crickets only as being as good as what they have eaten in the last 4 hours. One thing to keep in mind is that many chameleons will not cup feed, and may only do well with crickets presented as free-ranging. Other conditions may also inhibit the chameleon from feeding regardless of how the food is presented, and may need to be changed. A good sign of feeding is always a "healthy defecation", or some such terminology, and the build up or maintaining of healthy fat pads, especially on the top of the skull, behind the eyes. While I am sure you know this, for the benefit of other readers, don't rely on cricket counts to determine if your animal is feeding. Look for healthy dumps, and watch those fat-pads closely. If they start to reduce, something has to change. It may be the choice of food, or it may be a husbandry condition. Good luck with your chameleons.
Jim Flaherty
The Chameleon Company