You're right that bonus amounts would be a silly evaluation tool, but as a team who just spent that much money on him, I wouldn't be trading him 6 months into his development. After spending that much to get him, I'd want to be the one to develop him, at least for the first 2-3 seasons for sure.
That said, if he was a side piece in a more blockbustery type of deal, like for a trade involving someone like Luid Robert Jr coming back... sure. But certainly not as a piece in a rental reliever trade.