The three men are said to have contributed average monthly payments of $85 (Walter), $115 (Phil), and $140 (Justin). While the actual number of years is not completely clear, Justin assumes 20 years. He states cumulative total payments the men paid to Carla, "over 20 years, compounded at 6% interest, would come to $197,000." They also say that Walter paid $41,000 and Phil $47,000 over that period.
None of the calculated figures are correct. Assuming that the monthly averages are correct, as listed above, then the annual/lifetime contributions are $1,020/$20,400 (Walter); $1,380/$27,600 (Phil); and $1,680/$33,600 (Justin) for a total of $81,600.
Justin goes further in calculating accrued interest. He cites an annual figure of 6%. While this would have been approximately correct at the time of filming, it did not represent the previous 20 years. An average interest rate for 1948-1968 is ~3.28%.
At 3.28% the invested total for each man's contribution is $28,737 (Walter), $38,880 (Phil), and $47,332 (Justin). For a total of $114,950. This is significantly less than Justin's $197,000 figure (which is too high even at 6%, which would have been $157,000). [Note that $114,950 in 1968 has an inflation adjusted value of $949,600 in 2022.]
However, these are all theoretical. Presumably Carla used their money to buy the winery and that's where she made her money.
