Well, these are not the cheapest LEDs, indeed.
Humm, viewing angle 30°, is that enough?

... which is less than 250mA.
Assuming the flux.vs.current (there is no data for that range of currents in the datasheet) is not starting to derate at that current (which I think it will), you have around 3x the luminous flux compared to steady 70mA, so with 1:32 multiplex the percieved intensity of the panel would be cca 10% (OK maybe slightly more or less - the eye is not exactly integrating) of what can be achieved with these fine and expensive LEDs when driven non-multiplexed.
The cost of the drivers (we are using Toshiba, I don't know about the STxxx but assume they are cheaper) per LED is less than the cost of the LED (maybe 2-3x, depending on the particular dealer etc.).
Think about it.

Jan Waclawek