That is a completly unreasonable offer, a normal cards for key trade is 3 or 4 sets for a key or 40 random cards for a key, i have traded for ~10 keys for this ratio in the last month. Currently it is even possible to get more than 4 sets for a key in a trade.
Even if all cards are 5 eurocents each, when you count it's exactly 1.80 euro per key and on SteamTrades you may pick up keys at 1.80-1.90 dollars per key and this is similar price for key after you sell it on market.
40-50 cards per key is just standard (depends on buyer, I sell at 40-45 myself anyway) and anyone calling more then 50 is straight up demanding you to overpay.
I had a look at your cards, mate, and.. Well... I could choose 45 of the ones I'm seeing in your inventory now for 1 Tf2 key. Tell me if you'd do so and then I can make you an offer, my friend. Thanks :)
EDIT: Made an offer with 44 cards. . . Accept only if you want to. don't need to do a counter-offer. Take care :).
If you are interested send a tradeoffer here: https://steamcommunity.com/tradeoffer/new/?partner=87826631&token=A8HgRFaR
You can choose any of my cards in my inventory but foils count as 3 normal cards.
Currently i want 3 keys, that means i'm willing to trade 120 cards maximum.
I can also accept 14 ref for 40 cards;
I will accept a Tour of Duty ticket for 18 cards; i do not accept capsule keys.