72V40Ah, the energy is 72*40=2880Wh. The current energy density of lithium batteries can reach 200Wh/Kg, which is already very impressive. Let's calculate based on 200, the weight should not be less than 2880/200=14.4 kg. Basically, the weight is not less than 15 kg. This is a lithium-ion battery made of ternary materials. If it is made of lithium iron phosphate material, it will be very powerful if it can reach 130 Wh/Kg. The lithium iron phosphate battery is: 2880/130 = 22 kg. This is only the case for battery cells. If it is a module and BMS, structural parts, etc. are added, the weight will increase.
As for the price. Let's calculate the ternary battery at the cheapest price of 1.2 yuan/Wh. The price is 2,880 x 1.2 = 3,500 yuan. If it is a lithium iron phosphate battery, the price is nearly 6,000 yuan based on the cheapest price of 2 yuan/Wh.
The calculations above are tou relatively conservative and the values are relatively reliable.