So my questions are:
1. Is there any part of this spray schedule that looks like overkill?
2. How do you keep these costs down or is this just the price of owning a small vineyard?
I have 1/4 acre, 125 American and hybrid vines.
A few comments:
First: The first thing to note is the link you provided is for commercial operators. And the recommendations are to completely eliminate any issues across a broad range of diseases for commercial operators, be they a problem that year or not (only because they "might" be). After all, to a commercial operator, who may pick with machines, even a little gray mold brought into the winery would be a problem. But you are picking by hand, and you can just cut out that part of the bunch and toss the rest into the bin going to the crusher. In short, no need to be so "extreme" as commercial producers, as it is simply not cost effective.
Second: There are cheaper chemicals you can use that are not as "perfect" as the ones in guide you suggested, but do just fine, and well enough for the small vineyard for less. One example, the broad spectrum potassium bicarbonat product
Armicarb. Applied properly they do pretty well. If they miss something, for example, with botrytis you may have a few berries with gray rot, which really is nothing to worry about, just cut them out and move on at harvest, and if it is just noble rot, you can just use the grapes if you want.
Third: To save money spraying, you need to avoid simply follow a formula. You need to become a bit of a plant pathologist, know when conditions are most likely to cause fungus problems, and spray accordingly and only when necessary. Look up "integrated pest management for grapes" at your favorite search engine. And a good place to start is a guide from Agri-Food Canada (so applies to cold weather grapes):
Identification Guide to the Major Diseases of Grapes
Forth: As already mentioned, a lot depends on your local environment. Despite all I wrote above, you may need to spend a lot of money to keep the vines healthy. I would not call that typical, however. Rather just an unfortunate geographical choice for a vineyard placement.
Fifth: I don't use these chemicals listed in the link you provided. If you buy a gallon, how long does that last? How much is needed for 1/4 acre? How long can they stored? Ergo, are you paying $800 for 1 year or 5? (I know others here can answer this, I can not). Knowing that may affect long term cost calculations and budgets.
Finally: What do I have and what it costs me to spray (as one cost perspective). I have all Vinifera (thus no resistance to fungal diseases like some hybrids). Moist cool springs and falls, humid warm to hot summers. All spring, summer and fall averages 1-2 inches of rain a month (except in late July when the amount of rain can double). My vines and grapes would be wiped out from a variety of fungal diseases if I did not spray. I spend about $250 per hectare on fungicides a year. That would be about $25 for a 1/4 hectare. I spray mostly liquid lime sulfur (spring) and copper (spring and summer). Would love to use Armicarb, and other products (because Cu is not ideal), but not "approved" where I live (but are approved everywhere in the USA). Follow the link below to my web site, and you can judge the quality of my vines and grapes, given my spraying style and costs.