I foudn this is a post by Shadowood :
Gold Bars
-A Gold Bar is a resource produced only by players. 
-A goldsmith is required to produce gold bars. 
-Gold Bars are a required resource for many advanced constructions in Avonmora. 
-Gold Bars can be sold in the Market. 
Market Price
-Gold Bars market price price is based on Supply and Demand. 
-It changes dynamically in every 25 crates sold based on this formula: 
Gold Bars Price = -0.01 * Market Stock + 3000 
-A market fee is also applied to the price. The current market fee is 2.75%. This fee is calculated as shown below: 
Market Price = Gold Bars Price * 0.9725 for the market buying price. 
Market Price = Gold Bars Price * 1.0275 for the market selling price. 
Market price fee is calculated dynamically per 25 crates. 
-Duke bonuses of 2% is applied on sales. 
-There might be a voodoo bonus of up to 2.5% on sales from East Indian Company cards (Dutch, English and Spanish). 
The bonuses are applied as shown below: 
Final Price = Market Price + (Gold Bars Price * Duke Bonus) + (Gold Bars Price * EIC bonus) 
Bonuses are applied on the final price and are not calculated per 25 crates. 
Markets will always pay at LEAST 750 gold coins for a Gold Bars crate. 
The nation that holds the port, earns 0.75% on every Gold Bar crate sale. 
Warehouse Tycoon can play a great role in Gold Bars trading (up to 2.5% discount on manual purchases). 
So, a 100k bar sale will probably push the price way way down : but even if you got 150mil... thats only breaking even as with a GS20, your making price is just over 1500 per bar. Add in your 200 credits moving cost and its a major loss.