Offering 60% refund of the bet to those surrenders?

W/o any other factors like card counting, if someone holding 12 wants to surrender facing a 10, I think this is good to offer him.
E.g. the bet is $100 & I offer him $60. He’s got 20% extra of the return.
It also really good for me as if I win, I will get 133% of extra profit. If I have got a push, I still win 67% of the bet.
But what hand he’s got that we should not offer him like this?
15?16?
I am not very familiar with the probability & the return of this situation.

You guys may think no one takes this offer but I would like to tell you guys it really happened in Macau😂😂😂

Thank you so much!

Fred Renzey does a great job explaining scavenger blackjack in his book Blackjack Bluebook. When to offer to buy a hand, when to offer to buy part of a split, when to try and sell a hand, and so on. With the right players, this can be a very important tool.

Use one of the links here or here to work out the EV, and then you can use that to work out what you should offer (see below)

If someone had $100 bet on 13v10 or 17v10, and they wanted to surrender these hands, then you could offer to buy the hand for $55.

Note: This would be worth about +$3 in EV (if I worked it out correctly).
Note 2: Assuming you are playing "6-deck" and "American-style" hole card rules.