If this is the case I am thinking of, they are angry at the pastor because he was proselytizing, because he stepped away from Isla'am (his parents' faith) and, of course, because of his US citizenship. These are serious 'crimes' in a nation where the rule of law is based entirely on the Qu'ran.

He's being held in Evin (which is a massive hellhole where torture is the norm) and all reports suggest he's being beaten. Quite robustly, too, apparently.

The average price for a prisoner (Iran is cash-short and they do engage in kidnapping/ransom schemes, protestations to the contrary aside--they call it "bail" but we know what it is) is anywhere from a half million on up. This guy is rather high profile so they may want a million or two--maybe even more--for him. State won't pay but I understand this guy has backing from that lawyer who is active in religious cases at the Supremes. He has the wherewithal to put out the call and rake in some funding if they ever get to the point where they can negotiate some "bail," rather like they did for those hikers who supposedly strayed across the border (but who said they were abducted in Iraqi Kurdistan).

If he gets out, he needs to be told very clearly that he can't ever go back, ever, for any reason. I wonder if he had dual citizenship and traveled to the country on his Persian passport. If so, that further complicates matters, if the Iranians care to get shirtier than usual.

has faced increasingly severe consequences.

It seems that Iran could save itself some international trouble by letting him go but stipulating that he can't come back. I'm sure that is not what he wants, but he just needs to stay out of there for now.

He does have dual citizenship, according to what I have read, but I've no idea what passport he had been most recently traveling on.

I don't think they're afraid of international trouble at all, though. He's worth money that will be put to good use by a cash-poor and sanctioned government.

If I were a betting person, I'd say the "starting bid" for his "bail" is a million, simply because of this guy's high profile. It could very well be much higher. Part of State's job will be to try to knock down the price and find someone to act as the "payer" so our hands stay clean. If individuals raise the money, that's not an issue, but the US government will never pony up the dough.

I remember that one of our allies in the region (Oman, maybe?) coughed up the cash for at least two of those hikers that Iran kidnapped for ransom (that is what they did, despite their bogus sovereignty assertions), but it was probably more like a cash-kiting scheme (we sell them military equipment or construction/farming stuff worth more at a deep discount, they take the money saved and apply it to the ransom), so that we could maintain that we didn't pay ransom for hostages.

Is there no room for diplomatic negotiations in these cases?

negotiate with the ulema, and help to close the deal.

It's all about public deniability on both sides. Iran does not admit that they kidnap people for cash, and the US doesn't admit that they deal with Iran on any level, when they actually do, through intermediaries in the region who are our friends.