Already the Dunes have sneaked into a few Modern decks and it's seeing a fair amount of play in Standard. What's fascinating to me about Shefet Dunes is its price history. This was a $0.25 card that became a $0.75 card very quickly and quickly approached $1. It's still not too late to buy in as major MTG retailers like Channel Fireball and Card Kingdom are charging $1.49. (Shefet Dunes has also all but sold out on Amazon!) The TCGPlayer market is just a bit behind.
Whenever you see retailers charge that much more than TCGPlayer and eBay, it means they keep running out and have to keep buying. So, they have to raise the retail price so they can pay a decent price in cash or store credit to those selling spare copies to their buylists. This is why when you see buylist prices get really close to retail prices, something is definitely going on with that card.
What's the ceiling on Shefet Dunes? That's hard to say. The Ramunap Ruins only got to $1.50, and it's hard for many uncommons to go much higher. But uncommon lands can be funny. More than a few uncommon lands run up to $2 to $3 or even $4 out of nowhere.
Foils of Shefet Dunes aren't even twice as much in price as nonfoils right now. I'm not sure I'd put money into those unless you really want one. Typically low foil multipliers – that is, the foil price divided by the nonfoil price – mean that people aren't super high on a card outside of Standard, but it can also just mean that a card hasn't yet found a permanent home.
Really, Shefet Dunes is one of those incremental investments that become trade binder pieces rather than fodder for buylists or eBay. Whenever you look to add cards to your Magic collection, it's always good to have trade chips. These sorts of lands that can serve a purpose in a lot of different decks can be invaluable to have when you're trying to trade up to bigger chips or are looking to trade into new investments.
Always watch lands that have a steady demand profile like these, because you never know when the supply will dry up. The Shefet Dunes haven't really found many homes in Commander yet, which I find a bit surprising and I'm sure that will change at some point. It has value beyond Standard and is useful in just about any White creature-based deck there is. These Deserts are not really prime reprint material, and this one in particular hasn't ended up in as many places as they could, so invest confidently.