How much stardust is required for each type of trade?

Now that trading is available in the game, we are able to trade our Pokemon with other people. Trading a Pokemon requires a specific amount of stardust which is apparently more important depending on some conditions which are the following:

• One of the players do not have the traded Pokemon in his Pokedex.
• The Pokemon is shiny.
• The Pokemon is a legendary.

Now, how many stardust is required for each type of trade? I'm quite curious to know if the costs are cumulative if several conditions are met, for instance if each player is trading to the other a shiny legendary Pokemon that the other doesn't have.

According to the information on reddit, the following is the amount of stardust required for trades. The values are based on the "Good Friend" and will decrease as your friendship levels increase. The stardust required for the trade will be the same for both trainers, taking the higher value

Standard Trades - Pokemon both trainers have will only cost 100 stardust. I have confirmed this by trading a Pokemon a friend and I both have. The cost required was 100 stardust.

Standard trades cost 100 stardust

Special Trades - Trading Pokemon through a special trade will cost 20,000 stardust. I have confirmed this by trading a Pokemon I had and a friend did not. The stardust required was 20,000

Any pokemon traded with the criteria below counts as a special trade, which only 1 of can be completed per day

New Pokedex Entry | 20 000 Stardust

Legendary Trade | 20 000 Stardust

Shiny Trade | 20 000 Stardust

Very Special Trades - This is where trading gets expensive. If a trade is performed that meets two or more criteria for special trades, it will cost 1M stardust. I have "confirmed" this by attempting to trade a Shiny Charmander to a friend who did not have one, and it took well over 120k stardust.

Any 2 or more combinations of the above = 1 Million stardust

Eg:

Legendary + New Pokedex Entry | 1 Million Stardust

Any Pokemon you've never gotten Shiny before | 1 Million Stardust

While a very special trade may cost 1M stardust at the "Good Friend" level, a screenshot from Niantic's initial trade announcement indicates a "Best Friend" level will lower this cost to only 40,000 stardust.

I like this table as is very easy to follow:

The following friendship level discounts apply:

• Good friend => no discount (0%)
• Great friend => small discount (20%, 800k to trade)
• Ultra friend => medium reduction (92%, 80k to trade)
• Best friend => large reduction (96%, 40k to trade)

Source: A comprehensive guide to Pokemon GO Trading Mechanics and Rules