$8-10 total for the lands, $16-100 total for everything else. So an average of about $67, with an upper limit of about $110.
The lands have a smaller range since the only prices for them seem to be <$.50 or a small fortune, while decent cards of any other type could run anywhere between $.25 and $2.
Mind you, that's just at the time of building. Modifications over time that bring the total up I'd still say is a budget deck until you start going up over $200-300, since a couple $5-10 cards a month isn't exactly expensive.