Flash is not tough to learn, but a bit time consuming until you figure out the interface.

If it were me, and a client wanted it, I would tell them up front that you have to purchase software to achieve what they are after and then add the cost of the software into your billing. Not as a line item, but maybe like adding a couple extra hours or something.

There are also a ton of sites out there that cater to flash, and have lots of free scripts to offer. using what is out there really cuts down on the learning curve as you can see how things are accomplished.

Good Luck!