At what point does a 10 to 15 percent mezz coupon stop paying for the subordinate seat?

Mezz targets 10 to 15 percent. Common equity in the same deals is usually pitched at high teens and up. So the mezz lender gives up several hundred basis points of upside in exchange for sitting ahead of the equity, a contractual coupon, and a pledge that can be foreclosed on. The trade looks obvious at the top of the range. A 15 percent mezz coupon on a stabilized asset with a conservative senior in front of it is a good place to sit. At 10 percent on a transitional deal where the senior is already at 65 percent of a value nobody has tested, the case is much weaker. The lender is taking equity-shaped risk in the downside scenario, because if the property is worth less than the senior balance the pledge is worth nothing, and taking debt-shaped returns in the upside. The position that keeps holding up is that the number matters less than the attachment point. But serious people argue the opposite, that the coupon is the only thing that can actually be contracted for and everything else is a story about value. So which one binds the decision. Is there a coupon floor that does not move regardless of the stack, or is it attachment and last dollar exposure that decides and the rate is whatever the market gives?