Wow, looks like there are troubles with bake stands! I manage to make around 50 or 60 dollars, so here are a few tips.
-Go and make some bake goods on a weekend (preferably Sunday, there are more people off work) and check the newspaper. (It comes around 9 or 10 AM.) A popup should tell you about the baking report. Go to the park (near the fountain is best), put out the table and baked goods, and price the goods.
If a flavor says it is below average, make that around 7 dollars.
If a flavor is near zero, make it around 2 or 3 dollars. Also, don't waste too much time making this and only bake one plate. (Some sims will still buy it even if near zero.)
If a flavor is "the highest it has been in years!" make that flavor around 10 to 15 dollars. (Depending on the baking cost.)
-People usually start buying around lunch and dinner time. At night, people will be swarming for food.
You can also go into Switch Active Households in Edit Town and select a random family and take one of those family members to the park to buy from your child. Have that sim buy the expensive stuff.
To prevent long posting, I'll make a topic on this. Good luck!