rafiki said:
If you have negative prestige, no-one wants to talk to you.
Uhm, I think you mean, the better your relationship with the country in question, the cheaper you'll be able to get given deals?
I dunno...
today playing Belgium I had a terrible international rating (200th at one stage) due to quite a big national debt. The bad international rating was due to my terrible industrial score.
Anyway when I tried to open negoitiations with UK or anybody big, I was quoted £1,000!!!
However, once I finally realised that I wasn't using any tariffs

o, I eventually improved my international rating to 16th, industrial score to around 50 and voila, it was only costing me £150 or thereabouts to open negoitiations with UK or any of the great powers.
Whilst this was going on, my prestige hardly changed, but only gradually grew from 15 -> 29 (10 years).