I love courthouses and I do make them at times to aid in celebration. They are the only local-to-a-city way of making a content citizen happy (besides hiring entertainers). Surely in the scenario you described a courthouse makes more sense. In general there is a balance that needs to be struck here. Often the question is not a courthouse versus a low paying delivery but rather the main question that needs to be decided on a case by case basis is at what point do you deliver? Delivering early means smaller initial payoff but longer trade route benefit and less chance of your commodity falling out of demand.
Hmmm... so many questions, so little time.
1) The value of ongoing routes for celebration ?
2) When to build and deliver a given [demanded] van?
3) Whether to build and deliver undemanded vans?
4) The value of the ongoing route (ignoring celebration)?
I think this all started with 3), when I suggested that an [undemanded] van paying much under 65g was usually a loss. This led us to 1) and 4). I have already estimated the answer to 4) to be about 60g [I assumed the route pays about +3 arrows per turn, without rising much in the next 10 turns. I did not discount the 60g for the delay in delivery].
My first reaction to 2) is - do it ASAP. Since you said it was demanded, I'll assume we are talking about 125g or more here. I think I already discussed this briefly with Prof G before he got tired of me. The reason is that your payoff probably won't grow faster than inflation [usually about 5% to 7% in Civ2]. In other words, you are better off with a modest payoff that you can re-invest quickly. This advice does not apply in some special cases:
a) If you have limited gold for RBs, use it to get the best payoffs you can. So, you may have to delay the smaller ones, because there is no real choice.
b) I'm assuming you deliver overseas at a reasonable distance (over 20 tiles or so, I guess) otherwise you probably aren't getting a good return. Again, I don't see this as a real choice.
c) If your supplying city happens to reach size three, and starts to grow, just as your van arrives, then it may be reasonable to wait a few turns to deliver. But this is so rare, it is hardly worth mentioning, and I suspect that delivering immediately is not a big mistake anyway.
So, that brings us back to 1). After our latest posts, it seems there are many ways to celebrate, and the value of the ongoing route should not be greater than the costs of alternative methods that give the same result. Given this bound, I think we can treat ongoing routes as just a flow of arrows, much like any other arrows [actually less valuable than the ones from workers, since they don't affect initial van bonuses]. For "normal arrows", 1 arrow = 1 gold = 1 beaker works pretty well for most Civ2 decisions. Do you see any reason arrows from ongoing routes should be treated differently ? Anyway, if we can agree that "an arrow is just an arrow", it would simplify all this quite a bit. In fact, we could ignore 1); meaning replace it with 4).
Correct. The problem with discounting the routes is that you get some benefit right away (the extra arrows) but how much you need for continuing celebrations is very hard to predict. Furthermore, often the decision as to when to deliver is dictated by logistics of delivery.
Maybe we don't need to know, if the "arrow=arrow" idea seems OK to you.
Otherwise, can you make a very rough guess about the delay ? I think my games may not fit your idea well, since I rarely have cities over size 12. My rough guess is: Average delay = 15 turns. [I imagine a van in -200, which affects various celebrations averaging to approx +200AD ... about 18 turns ... but most vans come later than that, and affect fewer celebrations, with less delay ... so it seems fair to reduce the 18 to 15 ... I don't know if this right ... what do you think ?].