If you use the 'no playable shoppers' hack, also get his money order, and use that to control playables coming to the lot.
Yep. Thanks for the suggestion; I had forgotten about that fine tuning being available.
I did confirm the problem I had seemed to have something to do with the family funds of the affected families. When I played the affected family and increased their fundage, I then was able to complete the sales socials on the original lots. The amounts the affected families had were low, but not so low that they couldn't pay to get on the lot. And like I said these family members would sometimes (often even, if the price was reasonable enough) choose to pay on their own, without the sales socials.