Nope

1 man 1 hour
2 men half hour
4 men 1/4 hour

BUT
1 man 1 hour to paint a small fence
2 men half hour to paint a small fence
4 men can't paint a small fence because it's too small for 4 men to fit around

Is your question to do with time OR cost.

The cost is potentially the same but the time is obviously not.

I say potentially because
1 man only incurs 1 man's travel
2 men obviously incur travel for 2 men ( even if they're sharing)
4 men the same as above

Then there is the hidden cost
1 mans tools & 1litre of paint
2 mens tools, if you used 2 men does it mean 2 pots of 1/2L paint or 1L of paint and a paint scuttle. If neither do the 2 men become unproductive for a % of the time because they have to share the paint pot and hence its longer to complete the job, 30 mins is now more like 40 mins.

1 mans employer contribution to NI / Tax will be less than
2 men which will be less than
4 mens...

So you see...

It's not a particularly easy question to answer without a little more information.

The task and what's important to the employer.