If you want to exchange an empty cylinder for a full one, you only need to pay for the gas unless you have a 21 kg “old red” balloon (these cylinders are no longer filled or sold.)
The consequence of the efficiency of LPG systems is lower maintenance costs. An LPG forklift does not require expensive new batteries and the clean fuel means the exhaust systems can last much longer.
Note that lifting gas cylinders are intended for use ONLY on forklift trucks. These cylinders are equipped with an additional e. a siphon placed in the cylinder and through which the gas is provided in the valve in liquid form, not in vapor, as in ordinary cylinders.
It is prohibited to use such balloons for other domestic or industrial uses.