||I have seen this SO many times. I worked in the Accessories and giftwares trade for years and the Trade Shows are always Fri, Sat and Sun.
I like to go to the shows first thing Sunday morning because I try to give my business to those who are Shomer Shabbat and they are the ones who will come to the show early Sunday in hopes of making up for business "lost" on Shabbat.
EVERY time without rhyme or reason, those who close their booths for Shabbat are greeted with a mob scene on Sunday. I am the type to stop and ask the other buyers WHY they are buying from this vendor and at this time.
Over and over again, I hear the same thing. "I just had to see what was behind that curtain so I put off my buying until today", "I like to support a G-d fearing business person". Mind you the buyers are predominately Latin American and Caribbean Gentiles.
I have seen fortunes made in a matter of minutes as in the case of one dealer who had become Shomer Shabbat that year and he was sure the show would be a loss without the Saturday business. That Sunday morning he was literally mobbed with orders!! I watched him write $50,000 at 300% profit in the first 20 minutes! Hours later, his booth was still mobbed!
(I barely had a second to get in my "I told you so").
Another dealer I know, became Shomer Shabbat, closed his booth for the first time one year. He was discouraged because he was sure that it had cost him business. During the following year, he came up with a concept that made him enough money that he never even bothered to exhibit at another show.
I know a man in retail who is closed Shabbat and Yom Tov even though a Rabbi told him he could hire a Gentile to work his store for him because it is in a totally Gentile neighbourhood(but his FATHER told him he'd better not!!). This man has tracked his receipts faithfully throughout the years and he can show you that they are always double every Friday and the day or two before each Yom Tov.
Of course Shabbat observance is not a guarantee that we will be rich and successful, but our income is determined from Rosh Hashana to Rosh Hashana. Six days a week we work. We cannot earn anything by working on Shabbat. Afterall, if we cut a pie into seven pieces instead of six, we still have the same amount of pie in the end. The only difference is that we will not have Shabbat. And THAT would be no way