If it's a player I don't want, I'd accept 2. In fact an 18yr old DMC I had relegated to my bench for bad form and too many cards got me 5 tokens last season. I accepted that offer instantly. I would have even taken less, but this was really a no brainer since I wasn't going to use him anyway.
If it's a player I DO want, I wouldn't accept any offer, because I play to win, not to hoard tokens. You could offer me 1000 tokens for Cubillo (averaging nearly 50 goals a season now in his 8th season for me), and I would reject because he is not replaceable.
If it's a player i'm kind of on the fence about, like a 3 or 4 star backup with a good ability for example, I'll give him to you, but you have to pay, usually 3 tokens minimum.
Offer me 0 tokens, and I keep your tokens for 24 hours.
Offer me 1 or more, I'll reject if I don't want.
That's my general criteria for what I do with offers, and I suspect most managers use a similar thought process.
I more use the negotiations list to give players to friends among my Facebook group, but I do love to buy off it, not so much sell.