What herbs have the most yield per sq. ft. of planting?

What are the most efficient herbs to grow that have a high yield compared to the area they grow in?

Preferably medicinal.

I would vote for oregano.  Although thyme and oregano are about equal medicinally, oregano has a more vigorous growth habit and can grow as high as 18".  Thyme is a low creeper, rarely getting above 6', with much less biomass in its stands.  Oregano also crowds out weeds better.  Mine is even taking over from the centipede and Bermuda grass in the lawn.

saffron -check out how much it costs to buy

I'm just mad about saffron!

shhhh you are showing our ages

I vote for mint. It gets real dense and grows about 3' tall. Peppermint has more medicinal uses than other varieties.

Prune tall rosemary varieties, bay laurels, lemon verbena, ect into small tree forms and you could have a lower growing herb right up to the base and get double use of the space. I think there are actually many shrubby herbs.

Basil, if you have the right conditions for it. (Also, one can use up infinite amounts of basil. )