early_morning, I track between 20 and 30, just those discretionary expenses that are part of that budget. Examples: groceries, cat food & supplies, OTC health (eg, vitamins, allergy & cold tabs), coffee out, cigarettes (I smoke), vending, movies, concession, etc... things that are MY life. The hard budgeted items go on their respective spreadsheets: clothing, transportation, housing, debts, utilities, medical, gifts & donations. Think envelope method but just on a google doc.
But re the discretionary, I lump all the movies together, theater and rentals. Likewise, all coffees out go together. I *know* 7- 11 is cheaper than Starbucks, I don't need to see it on a spreadsheet. I know concessions are higher priced at the theater. When I saw how much I spent in one month, I became much more conscientious of taking my own.
It takes a moment to log it into my notebook. Maybe an hour to tally at the end of the month and enter it onto the spreadsheet.
Re the cost of product X at Target v. Kmart, it may be better to track those in a price book. I also use Google docs for that. Track the products you use most regularly so you can tell whether it's really a good sale. I've got it set up the same way as Amy Dacyzyn suggested in Tightwad Gazette but, obviously, with Google Docs it's all accessible on my phone.
I lost a lot of hours over the years, starting this spreadsheet or that. Too crazy and time consuming to maintain. A little time each day and then at the end of the month provided more useable info for MY life to make smarter changes. That's why we budget, right? To live our lives within our resources, not to sit in front of a computer contemplating whether to create another category of catfood Y and catfood Z because one may save us .00009 per morsel and in reality the cat will only eat catfood X so time and money wasted anyway.
Hope that helped.