Cost of a Napoleonic army

I decided a while back to take the plunge and start a 28mm Nappy army to play the period with my friend Paul. The choice of nationality was easy, as Paul had no British, only French, Prussian, Dutch, what have you.
So I would do a British army, which suited my requirements exactly. (If I wanted to use them for other games I can always use orcs, fishmen or space aliens as opponents.....what?) The minimum worthwhile force I decided would have to be:

2 infantry brigades each of a mounted command, 3 line battalions and 1 light (skirmish) battalion, plus an attached artillery battery each.

1 cavalry brigade of 4 cavalry regiments plus an attached horse artillery battery

An army command.

Now to cost. Each infantry bn if bought separately will be £22-£25 (more on this later) so the major part of the 2 brigades alone will be £200. Depending on where I get the cavalry and artillery the cost per unit might be more, pushing the total cost for my small force to perhaps £500. I doubt that the whole of my 20mm WWII collection of 6 different armies will total that much!
However, it is not really the amount of money that is a huge issue, as it will be acquired a unit at a time perhaps one a month. As always it is far easier to spend money than it is to find time to paint and base.