Repayment of Shabas expenditures

Question

Betza 15-16 says that one's allotment of money for the year doesn't include expenditures for Shabas and yom tov, for which one is repaid according to his outlay. (First off, am I reading that right? But I assume so, so that's not my main question, which follows.) What's included in this?

• Expenditures for anyone (oneself, one's family, one's guests, one's hosts (bring a bottle of wine when you go for a meal), anyone at all)? Donations to tom'che Shabas?
• Expenditures on anything (chulent meat, precut toilet tissue, candlesticks)?
• Rentals (tables, chairs)? Services (waiter)?
• The Shabas portion of stuff purchased for general use (one seventh the price of a canister of salt, or, combining with the subquestion above about non-food items and services, one seventh the price of a house or medical aide)?
• The Shabas portion of food cooked for Shabas but with leftovers eaten during the week?
• The weekday portion of food cooked for Shabas but with leftovers eaten during the week? What if one made extra so he'd have during leftovers for the week? Or what if none of it actually got eaten on Shabas (say, you forgot to serve it)?

With sources, please, where possible, of course.

Answer 1

The Shita Mekubetzes mentions in the name of the Ritva that the "Divine reimbursement" applies to expenses of all mitzvos, and that Shabbos, Yom Tov, and Children's Torah education were chosen as examples because they are common and regular.

There is a parable of a wealthy man who has two married children. One child is very wealthy while the other one is poor. The father sends out invitations to the two children, inviting them to come visit him in honor of a third child's bar mitzvah. The father asks that, in his honor, they buy new clothing, and that whatever they spend for this, he will repay.

The wealthy child spends a fortune, adorning himself and his family in the finest raiment, while the poor child is unable even to borrow the amount needed to buy the simplest of new clothing. After the bar mitzvah, the wealthy child presents his father with a hefty bill, which the father refuses to pay: "I promised to pay expenses incurred in my honor," says the father. "Had you been concerned with my honor, you would have seen to it that your poor brother attended the bar mitzvah in new clothing. As it occurred, he arrived in rags."

So too, G-d promises to reimburse you for what you spend for Shabbos and Yom Tov; but only if you prove that you are doing so to honor the Shabbos, by providing for the needy and the poor just as you do for yourself.

http://ohr.edu/ask/ask207.htm#PD

Answer 2

I just saw the following in בית ומנוחה, a (Jerusalem, Kislev 5759) compilation by his son of speeches and letters of ר׳ משה אהרו שטרן, the late mashgiach of Kamenitz, on page 137:

זכורני שבירושלים היו נוהגים אנשי יראה, שהיו מרבים בקניות לצורך שבת, במדה כזאת שהיה נשאר לחצי השבוע הנוסף, באמרם הרי הוצאת שבת ויו״ט הם חוץ ממזונותיו הקצובים, א״כ למה לא נרבה כבר בהוצאה וישאר גם לימי החול, וכל זה היא בכלל הוצאת שבת ויו״ט. כשהיו צריכים לקנות נעליים לילד היו מחדשים ומלבישים את הנעליים לכבוד שבת, כדי שיהא חוץ ממזונותיו הקצובים

Or, in my own loose translation:

I recall that, in Jerusalem, God-fearing men would purchase much for Shabas, a quantity that would allow leftovers for half the next week, saying "expenditures for Shabas and holidays are outside of one's allotment of livelihood, so why not spend more so that there'll be leftovers for the weekdays, and it will all count as expenditures for Shabas and holidays". When they needed to buy shoes for their children, they'd put the new shoes on the children for first time in honor of Shabas, so that it would be outside of one's allotment of livelihood

He cites this with approval. Several of my six subquestions seem to be (at least partially) answered by this. In order:

• At least for one's dependent children.
• Even shoes.
• [Not answered.]
• Even the weekday portion of stuff purchased for general use, as long as it was purchased with Shabas in mind and used for Shabas. (Or something like that.)
• Yes.
• Even if one bought extra so there'd be leftovers.