i just started a commercial winery that will be open in '11. even with my model, it's not a cheap endevour. there are many laws and regulations on top of insurance and permits to buy. it's has not been easy to say the least. we don't plan on getting rich.
i've heard, "if you want to make a small fortune in the wine business, start with a large one."
there are certain fruits that are more profitable. the key is price of fruit per gal of wine and don't skimp on flavor. so, it is feasable to buy pears at say $1.75 and you need about 4-6 lbs minimum. at 6 lbs/ gal you have a wine that is $10.50/gal of wine. there are 5 bottles per gallon and you see that it's about $2.10 for just the fruit. with all the other things to make a bottle, it's about $3.15-3.30 per bottle. then you have to manage overhead and tastings. or you could just try and sell it retail without tastings as tastings are supposed to take about 7-10% of your wine.
not to mention you have to buy tanks, heat/cooling for a building, water, waste (and believe me there is alot to deal with there) and run a tasting room to boot!