Likewise for Dota 2 players. Some of those old / early cosmetics have shot up in price. A friend of mine I used to play with had a $500 item. Getting rid of them may fund your game purchases for a bit.
There are plenty of sites out there that can give you a value of your inventory. Just make sure your privacy settings for your inventory are set to "public": https://steamcommunity.com/my/edit/settings (though I'd recommend changing it back to private after you use one of the tools, since scammers will try and target you if you have public high value items).
> Some of those old / early cosmetics have shot up in price
"Back in my day" you brought your own skins, maps, and mods to your clan's Quake 2 server and they'd be automatically copied-into other players' q2base profile directories when they connected: free and fast. Making skins in a cracked copy of Photoshop 5.5 or PaintShopPro (don't forget to save to PCX!) was trivial and because nothing really mattered no-one could possibly get angry at anything.
...but now you're telling me that if I want to add custom skins to CounterStrike I have to pay other people hugely inflated sums for the privilege of something that was still free and open to all only yesteryear? And we're surprised at how toxic the "gamer" community has become over the past 15 years since tradable lootboxes, cosmetics, and microtransactions became the norm?
There are plenty of sites out there that can give you a value of your inventory. Just make sure your privacy settings for your inventory are set to "public": https://steamcommunity.com/my/edit/settings (though I'd recommend changing it back to private after you use one of the tools, since scammers will try and target you if you have public high value items).