For the most part, short routes = more frequency due to more competition. Unless you are in Japan, you don't fly widebodies on 200nm high density routes--you use several narrow bodies at high frequency. It sure would be nice to pay one crew to fly a 300 seater 1x daily, but instead you have to pay 3 crews to fly a 100 seater 3x daily. Thus, the staff costs are inherently higher.
The longer the flight, the less competition one will face because these routes require more expensive aircraft with more fuel burn etc. They usually involve flying to congested airports with high slot costs as well. So in the end, short routes are more profitable, but they are very vulnerable to new entrants and DO require significantly more staff to operate already.