That's a really sorry control because you don't have any way to account for variables such as lack of or incorrect maintenance practices, wear and tear due to different local climates, rider weight, etc.

A better way to perform this experiment would be to purchase two bikes at once, one "real" bike, and one BSO with similar drive trains (i.e. both single speed, derailleur, igh, etc.) and trade off commutes, that way most variables would be accounted for easily.

If you wanted to use our group experiences as a control you'd need some way to statistically quantify them to make any measurement against them meaningful.

As it is, this thread is simply a blog of how many miles you've put on a decent-quality low end bike, and you've made the revolutionary discovery that cycling is a cheap way to commute.