IS it time?

Card prices are in a standard low of between 2-6 US cents per, with the exception of foils and even then buyers want to cheap out on those.

Card prices fluctuate a bit, and particularly around the time a lot of people get a game they might temporarily drop a fare bit in price. But they rarely seem to go up much in value

Steam takes % of every sale, same does publisher of every game, and these are always rounded up to lowest value possible (ala 1 cent for USD) so like BHTrellis188 said above, with cards costing 0.03-0.06 you will be gfetting 0.01-0.04USD - aka paying 30-66% "tax". Usual tax is 15%, so it's much better to sell cards in lower denomination currency. If you realy have serious amounts of cards it would be most porfitable to set up alternate account (for example using VPN) trade all cards there, and then you can buy gifts for yourself, or if region prices differ too much send yourself wallet code for money you got. You will still earn 15-40% more ;)

How would one sell them in bulk?

there are tools like Steam Economy Enhancer which help a lot with this

Depending on how fast you want to gain your games.If you have time to spare you can gain a little bit of profit for each trade you do with cards.Most common practice I saw was 1(yours):1+something(a random card/gem/case whatever).I actually sell and buy unmarketable trading cards(acting as a middle man) and with a little bit of patience I was able to buy
911 Operator+dlc(X2)
Duskers (X2)
Red Faction Guerrilla Re-Mars-tered(X2)
Paratopic (X2)
Pool Panic(X2)
Shadow of Mordor
If you want to have your games instantly ready for you I suggest just selling the cards on the market and you should be able to get a decent amount of money(depending on your cards)

I hope this helps.Hopefully you will get the past the current problem :D

If you get the Steam Inventory Helper add on for Chrome you can bulk list cards. You can list them pages at a time but FYI I`d do them a page or 2 at a time and give it a couple of minutes to load up card prices b4 clickin the sell button.

I'm no trading card expert, but "huge collection" makes me think of some bot farm with hundreds of thousands of cards. A few thousand trading cards just aren't worth much.

Keep them if you want to keep them. Sell them if you want to sell them. Nobody knows what they are going to be worth tomorrow. Sometimes the developer of some Steam game is a bad boy and Valve make all their stuff non-marketable, at which point you're unable to list them on the market and must find a person willing to trade for them.

Sometimes people see their foil card listed for $50 on the marketplace and think cool, I'm gonna buy a new game! But a dreamer listing their foil card for $50 doesn't mean it's worth $50. It's worth whatever someone is willing to pay, maybe 50 bucks but probably not... If you check the history you might see it's only ever sold for 20 cents. :)

There are browser addons to unload cards in bulk but I've never tried using one so I have no clue there, sorry... :(

If you don't use one of those things, and don't sell them in bulk to some trader, you'll be clicking each card by hand, confirming all of them... Ask yourself how much your time is worth... :) A bit of clicking for each card, a few cents per card * a few thousand cards = a lot of clicking, and a little bit of wallet money for the Steam sale. Sort your wishlist and you could probably get a few cheap games, just don't expect too much.

Sorting your steam inventory by price can be helpful with this Item Value Sorter tool

well, if you wait till late november, you'll be able to gain 20-30% from selling it

Well if you want to make money fast, you can sell them all for 0.02 disregarding their value and you get about 80 euros. But you could check out each card's price if you want and maybe make more money

I have no idea how accurate this is, but it says your cards could sell for $167
I also don't know how easy it would be to find someone who would bulk-buy it or for how much...

Time, Mr. Freeman?

1. just sell it, increase/drop in price is relative so i dont really know. but from what i know, when the game is banned, it's relevant cards cant be sold
2. none, except when you want to craft badge for lv up
3. Steam Inventory Helper

by selling cards, i never buy in steam store again, ever!! except bundled games on other store that is

Steam Economy Enhancer is a TamperMonkey script that will easily automate selling all your cards for you. It'll automatically set each card to the current selling price.

I would just sell the cards and not worry about it. You'd be surprised how much money you can get, even at $0.02 per card. Across 4000 cards you're looking at $80+.

first of all, wish you a good recovery!
Maybe you don't need to buy new games, because you got so many you might just check out the ones you already have ;)