It's arguable that without duel lands Legacy would actually be cheaper than Modern. The larger card pool creates more variety where fringy cards that aren't worth a lot can find a home in a deck. If you look on MTGoldfish at most of the Legacy decks they would be in the 500-800 range, if not less, if it wasn't for the duels. Compare that to something like Jund in Modern, and there's barely a card below 20 dollars.
Just something of note I've found interesting. It looks like despite the selective reprinting the price of buying into Modern is actually going up.
Just something of note I've found interesting. It looks like despite the selective reprinting the price of buying into Modern is actually going up.