microeconomic theory applied to picking fraterniti

In terms of microeconomic theory it is only worth it to join a top tier fraternity.

For this proof:
Inputs are finances and time
outputs are hot women and good parties

A no-name fraternity exhibits economic inefficiency, as there is the sunk cost (expenditures that will be spent regardless where you pledge). Also to keep in mind that time is an input. The opportunity cost (the next best alternative) could be instead of time spent pledging, you could be studying or dieting/working out.

No-name fraternities exhibit diminishing total returns as increasing the inputs actually yields lower total output, output being hot women and good parties.

(For all intents and purposes, hot women are considered DG, DZ, AXO, Pi Phi, Theta and Alpha Phi)

Increasing these inputs would be increasing total cost proportionally, and as a result, you would be in the uneconomic region of the isoquant with absolutely no way to change your decision.

If you don't understand, only rush a top tier fraternity. The isoquant level for a top tier is significantly higher for a top tier than a low tier for a nearly equivalent level of inputs.

With all this in mind, FIJI, Phi Psi, Sig Pi, Theta Chi, Phi Tau, KA and Phi Delt are the only ones worth rushing.