Not exactly, although there are often expectations re sizing (grading) which infers a certain number (nominal) per carton or bulk package. Not how potatoes might be sold, but punnets of strawberries etc are first packed by weight per punnet and punnets per case. Similar for trays of mangoes where the grading by size gives a consistent number per tray. Similar experiences to @grahroll (packing on farm small cropping) items by bunches per case etc.
Some stone fruit (premium), apples etc can be wholesaled carton packaged with a moulded (recycled paper pulp or plastic?) tray one per hollow. Multiple layers.
I should have also said that some fruit and veges are traditionally sold by the item, not by weight. So a banana or an apple isn’t something new - just new for the fruit/vege in question. Things like avocados, bunch of asparagus, cauliflower head and celery have been sold traditionally as per piece rather than per $/kg.
On the flip side, I have seen many green grocers now selling items which traditionally been sold as a piece as $/kg (including asparagus, avocadoes, cauliflower and celery). When I have struck this, I generally take the product to the scales, weigh them and work out in my head a rough conversion to per piece. Sometimes the $/kg works out reasonable/cheap, but other times slight more than I am willing pay.
The fundamental overall issue is the cost per Kilo of things. Regardless of if shown per each, the overall price is per Kg is what you are charged.
Per kg is the main way to compare between sellers. e.g. Coles has capsicum for $4.90 per kg and Woolworths has $1.03 each but no cost shown for per Kg or how many in a Kg. When you are in store the price is per Kg ( never shown as each) and shows as $9.90 Kg
Things that have always been sold as a bunch or each such as celery, spring onions are an exception.
