Selling crickets by number and age is fine if you are going to feed them to your pets. But it is not the information we (people who practice entomophagy) want. We want to the total weight of the crickets we are going to buy. This is how food is typically sold. The package of walnuts in my kitchen say “Net Wt 12 oz (341 g)”. This practice should be adopted when selling edible insect for human consumption.
Another consideration is the general size of the crickets. I recommend getting away from the “weeks old” categorization. Describing a chicken by its age at harvest is kind of weird. I think there are better descriptions we can use. The shrimp industry uses a number per pound system. “21/25” means that there are 21 to 25 shrimp per pound. The insect industry could adopt a similar system. For example a package of crickets might read:
Net Wt 12 oz (341 g)
Size: 200-250 crickets/lb
Shrimpers also use categories like jumbo, medium and tiny but these adjectives are somewhat open to interpretation and aren’t recommended.
Many insects undergo physical changes during their life cycle. For example crickets grow wings at about 4 weeks old. Categorizing based on a well-defined attribute could work. A producer could sell 2 varieties… “Adult Crickets” and “Wingless Crickets”.