I doubt that any starting point would be that low.
The MAC report states the following :-
Under the assumption that housing costs are zero, the equivalent current gross income threshold would be £5,500 per year.
Under the assumption that housing costs are £119 per week, the equivalent current post-tax income threshold is £224.95 per week (i.e. £105.95 plus £119).
The equivalent current gross income threshold is therefore £264 per week, or £13,700 per year.
The above assumptions are for a childless couple.
The current "financial test" is generally based on income support levels, which for 2011/2012 are set at £105.95 per week. Means the sponsor needs to show that amount as available for discretional spending.
This was largely arrived at by tribunals and legal system.