No, the Excavator isn't a big money card and he's more of a role player in the right deck. Still, he's a nice card to have around, even if you only need one or two copies per deck. I really like his long-term potential, though. Could he be a $10-12 card in the future? I'm more thinking $5-7 if a Modern deck really goes to town with him as a major contributor. Already, buylists are paying a wide range for this card from $0.75 all the way up to $1.75. There's real demand for this card, and don't forget that this card is extremely good in Commander!
Right now, Ramunap Excavator is just a cute inclusion in Green/White and Green/Black Collected Company decks to replay fetchlands. He sees play in some Legacy decks, too, but Legacy is not as big a factor in paper Magic anymore. But there's so much potential with this guy. Just being able to replay one fetchland with his ability is pretty nice. Heck, Ramunap Excavator even lets you reuse budget fetchlands like Evolving Wilds and Terramorphic Expanse!
While there aren't any straight up combos with Ramunap Excavator, this guy does have good synergy with cards like Exploration and Oracle of Mul Daya that allow you to play an additional land on your turn. Even Dinos have Wayward Swordtooth to let you play an extra land. Too bad Summer Bloom is banned in Modern, because the Excavator would certainly be included in that deck.
I love real estate in Magic, and any card that lets you replay lands is essentially making more real estate out of nothing is valuable. Look at Life From the Loam and especially Crucible of Worlds! Who doesn't want to play their Wastelands over and over again in Legacy, Strip Mines and other land destruction cards in Commander, and fetchlands, Ghost Quarters, and Field of Ruins over and over again in Modern? I love this card, and keeping four of them on hand is a great investment.