I'd almost go the other way Wolfe. Yes, Modern has a higher initial cost, but staying relevant in Standard gets expensive fast. At least with modern, you can build a deck and, assuming you build a decent one, stick with it for a while. Yes, you might make small changes once in a while as new cards come out, but a lot of modern staples are largely unchanged in a long time.
Heck, you can build an infect deck for <50$ that can beat 1000$ goyf decks pretty easily. Standard's rotation makes it expensive to stay up with. I usually buy a box on
release (didn't for oath because I just bought a house; money was tighter), but even then I don't get one of everything (although I'm usually only a card or two off a playset for commons and have most of the uncommons.) That's what, 300$ a year? And not that far down the line, those cards fall off and you can't use them anymore in Standard.
Just my two cents. I like standard, but I'm quickly becoming more focused on Modern decks for longevity.