These are the current price Fluctuations in my save game Haut-Beyleron. As i don't know yet if these change during the game and/or differ from map to map, feel free to comment.

So Far i noticed these price fluctuations are the same on each map, yet as of now they are incorrect sometimes with prices being at it's highest during other months. Also Prices seem to be random each time you start/restart the game.

Highest Prices
+Wheat
+Barley
+Oat
+Sorghum
+Corn
+Potatoes
+Sugar Beet (Normal/Cut)
+Wood Chips
+Silage
+Grass
+Hay
+Straw
+Flour
+Bread
+Manure
+Slurry
+Digestate

Lowest Prices
-Raisins

Highest Prices
+Silage
+Grass
+Hay
+Straw
+Grape Juice
+Lettuce
+Tomatoes
+Strawberries
+Chocolate
+Manure
+Slurry
+Digestate

Lowest Prices
-Soybeans
-Sugarcane
-Sugar

Highest Prices
+Sunflowers
+Cotton
+Honey
+Cereal
+Sunflower Oil

Lowest Prices
-Sugarcane
-Sugar
-Planks
-Furniture

Highest Prices
+Nothing,Fabric and Clothes are Rising

Lowest Prices
-Eggs

Highest Prices
+Grapes
+Wool
+Fabric
+Clothes

Lowest Prices
-Nothing at it's lowest price, If you don't need the money hold on to your wares and wait for a better time to sell.

Highest Prices
+Olives
+Olive Oil
+Chocolate

Lowest Prices
-Cake
-Butter
-Cheese

Highest Prices
+Soybeans
+Corn
+Sugarcane
+Sugar
+Planks
+Furniture

Lowest Prices
-Canola
-Sorghum
-Potatoes
-Sugar Beet/ Sugar Beet Cut
-Wood Chips
-Silage
-Grass
-Hay
-Canola Oil
-Grape Juice
-Manure
-Slurry
-Digestate

Highest Prices
+Nothing

Lowest Prices
-Wheat
-Barley
-Oat
-Sorghum
-Potatoes
-Sugar Beet/Cut Sugar Beet
-Wood Chips
-Silage
-Grass
-Hay
-Straw
-Flour
-Bread
-Manure
-Slurry
-Digestate

Highest Prices
+Sugarcane
+Sugar

Lowest Prices
-Cotton
-Honey
-Cereal

Highest Prices
+Milk
+Cake
+Butter
+Cheese
+Raisins

Lowest Prices
-Grapes
-Wool
-Fabric
-Clothes
-Lettuce
-Tomatoes
-Strawberries
-Chocolate

Highest Prices
+Eggs

Lowest Prices
-Olives
-Corn
-Olive Oil

Highest Prices
+Canola
+Canola Oil

Lowest Prices
-Sunflowers
-Sunflower Oil