Don't make the assumption that the builder charge for the option has anything to
do with his cost. As with options on cars, options on houses are designed to
increase the margin on the entire sale.

And not just the builder. Upgrades is where sub-contractors make their
money.

Extra cable TV and phone boxes can go either way, depending on the design of the
house and how hard it will be to fish cable through walls.

True, but here in NJ, buiders are usually pretty reasonable with prices
on those. An extra phone jack in both cases cost me $60, a lightswitch
and fixture - $130. Not worth the headache later, IMO.

They frequently have discretion to do
things without getting the office involved.

If you know someone like that, let me know. I may buy a house there
just for that reason ;-)