Well the demand runs on the law of diminishing returns. So if you have more frequencies, you have to charge less to fill your planes, so that means you don't actually make twice the amount of money from 2 frequencies as 1. You make more like 1.7 or 1.8 times. And then if you have 3 frequencies, you make 2.3 or 2.4 times the amount of money. And so on and so forth. So you'd be best served doing one frequencies to more destinations than doing multiple to one.
You make more money on a per-flight basis on one frequency.