$450 USD open market used
The RPD is a belt fed, air cooled machine gun which fires from an open bolt. It uses the same 7.62x39mm cartridge used by the SKS and AK-47/AKM rifles. For political reasons, it was replaced in service in the Soviet Union by the RPK-47, which is a heavy-barreled version of the AK-47, but the RPD was widely exported, and was also manufactured in China.
1000-100000 USD
Anywhere from $50-$250
Around $5,000 for a LEGAL, transferrable MAC-10.
The Scar - L Costs $2700 USD
Depends on the machine gun. Anywhere from $100 to several thousand dollars
During World War I, the cost of a machine gun varied depending on the model and manufacturer, but a typical price for a machine gun like the British Lewis gun was around £25 to £30 in 1914, which would be equivalent to several hundred pounds today when adjusted for inflation. The more advanced Vickers machine gun was priced similarly. These costs reflect the significant investment nations made in heavy weaponry during the war.
Currently it is not a weapon that is identified as being available. The related link provides a list a confirmed weapons. No, but the the RPK light machine gun will be available to use in-game.
Anywhere between 200-thousands of dollars depending on tpye.
materials, cost,
$2150 USD in 2014
Machine gun is a much broader category, which includes both current and obsolete models. The Maxim gun is a specific type of machine gun, and an obsolete one, at that.