Caveat emptor baby.. I have bought things in such shops with ultra low prices. But I spent close to 5 hours in that shop trying to understand where the trick is. Or how they will make a profit. If I can't understand, I just leave.
If it's just a single item, I usually conclude they are stolen items. If they have multiple units, I try to ascertain the country of origin/warranty status. I also spend a lot of time inspecting the unit to a point wataniambia "Kama hutaki kununua stop wasting our time"
I also try to determine their customer care skills/patience with solving problems.
Ukikaa kwa a fake shop like for 3 hours utapata customer amekuja na complaints/police and you can walk away.
Caveat emptor. Caveat emptor! CAVEAT EMPTOR BABY!