There is a point at which a lower price has a negative
effect on sales. People don't take it seriously. As Allison
pointed out, there were cheaper BASICs available. Why did
anyone want Microsoft's?
Using a slightly different - and, indeed, almost invisible -
marketing strategy, millions of copies of Microsoft BASIC
were sold - one inside each and every Apple ][+, ][e, and //c,
for example.
I'm sure Bill was smart enough to realize that
gaining
1,000 customers at $50 leads to quite different administrative
and tech support requirements than 100 customers at $500 each.
And who knows how many copies were sold?
MBASIC was also commonly bundled with many of the popular
CP/M boxes of the late 70's/early 80's. This is probably
a couple million more copies.
Tim.