For 6T for 4 days its not worth, because later I will probably pay another 30T or so. For that the player is not good enough and I don't care so much on this account, the weak player can also play.
I think the offers depend on your average team quality. And like always, the prices rise exponentially. It's like with recommendation, the lower guys are much better than the high end players for 700 token.
As I said, that kind of players currently costs at least 50 tokens on auction. So 36 tokens is still a good deal as he's a fast trainer and you don't need to spend time on auction to find him. As you say the offer depends on the average quality of your team. If they refresh the offer i would try to put on my reserves to see if I get a good offer as this.