1. It's the most popular sport on the island
2. Any performance improvement in FC IOM will boost players in the Manx leagues
3. If FC IOM progress into higher leagues, more away supporters will travel over and boost hotels / restaurants / bars etc and boost the economy through the winter
4. A successful FC IOM team will boost home support / income and will improve the 'feel good factor' on the island
5. A successful FC IOM team will give younger players exposure / opportunities to play at a professional level in the uk
If FC IOM can progress up the leagues, and hopefully get into the English National League, i'd estimate away support will be a significant figure. Teams like Aldershot, Notts County, Southend, Chesterfield, Oldham etc will bring 400 / 500 supporters (yes, an increase in capacity will be required) over twice a month, and they will need a hotel and they will have a night out. 250 away fans spending £200 for 23 games is over £1m going back into the ecomomy!! Many will stay the weekend and hopefully tell their friends how wonderful the Island is, and boost tourism even further.
I would imagine a turnover of £2m would be required in the EFL. 2,500 through the gate at £18 will give an income of £1m, shirt sponsorship £500k??, ground sponsorship £200k??, government sponsorship £500k??, TV money ?, FA Cup prize money?