As you may or may not know, signing up for Amazon's paid-for subscription service Prime grants you access to its Twitch Prime counterpart free-of-charge. The latter in turn offers subscribers free monthly loot which last month saw PlayerUnknown's Battlegrounds players treated to jeans, t-shirts and "stylish" ski masks.
If you collected said freebies and enjoyed them, that's great. If you collected them but didn't open them, however, you might be worth a few quid.
"I noticed PUBG had some marketable items and was shocked when I saw the PUBG twitch loot was marketable and the the lowest price it was listed at was $30," explains hollomat. "I wanted to sell it immediately to get credit for Pyre and checked out the highest buying price which was $25. I listed it and it sold immediately netting me around $22 in steam credit."
At the time of writing, these numbers have jumped to $28.49 and $23.25 respectively.
At present, Twitch Prime is offering Overwatch and Warframe loot which means if you missed the PUBG offer it's for now gone. If you have Twitch Prime, have PUBG, have claimed the former's free loot and have activated it but haven't used it on yourself—then you're good to go.
As hollomat points out, a combination of this criteria, demand, and an increasingly popular game appear to be driving the price up. Act fast if this applies to you.