'per kg' is correct and usable in written English.
You can use it to indicate the price of something per kilogram or the quantity of something per kilogram. For example, "This product costs €2 per kg."
The carton has 4kg less embedded carbon than conventional polyethylene on a per kg basis.
Conventional alternative: £6.25 per kg for ungrated.
Cost: Works out as £3.60 per kg.
★★★ Neal's Yard Dairy Colston Bassett £22.90 per kg That's bizarre!
This year, prices reportedly soared to more than $200 per kg, up from $20 per kg five years ago.
Witch costs £7.60 per kg, enough for five adult portions, compared with £11 per kg for cod.
Try the smoked mussels (from $5 per kg).
China's food safety standards rule that rice can contain no more than 0.2 mg per kg of cadmium, and the international limit is 0.4 mg per kg.
Horn from African rhinos is worth£1,300 to £3,300 per kg, and horn from Asian rhinos up to £32,000 per kg.
It cost him £22 per kg instead of the usual £14 – but he doesn't seem bothered.
Their harvest sells for 100 rupees (£1) per kg in local markets.
