Hi,
Don't know which firm you're interviewing with but I would suggest the following:
1). Figure out the potential revenue streams for the program, let's say it's for the Olympic, I would say major revenue streams are tickets sales, advertisement, entry fees from each partipating country(?), interviewers may ask what else here, so make sure you're creative, you can even further struture it by categorising them as direct and indirect revenue streams
2). after you have a clear list of revenue streams, you can estimate the revenue for each stream, for some it maybe market sizing, like ticket sales, then you usa the market sizing approaching (1). demand/supply 2). formula 3). assumption 4) calculation 5) sanity check) Due to time conern, very likely you don't need to calculate for every revenue stream, interviewer will pick one for you
3). Then you add up everything and maybe make some adjustment base on your judgement of the reality
Hope it helps!