Cheaper, they claim. Well, now, what if we calculate the 25,000 years for guard duty by, say, a small army of 5000. Say they're being paid $50,000 a year with no inflation adjustment. That comes to a paltry $6 trillion just to take out the garbage.
Finding technically competent employees is a dismal consideration. The things must be operated carefully and everything treated just so. The remnants will be around for millenia. But who's studying nuclear engineering? Who will run even the existing plants in a couple of decades? That's a scary concern.
Safety is scary, too. I visited the Olkiluoto reactor complex in Finland a couple of years ago, including a waste depository way below sea level. It contained huge concrete cylinders full or part full with mid-level waste from the reactors and we saw the copper cylinders for interment of the fuel assemblies. These are to be packed with benthonite clay to keep out intruding seawater. We were told they were already pumping 8000 gallons of sea water per hour out of the rad waste pits. The facility, they said, is one of two like it in the world, the other being at Yucca Flats, Nevada. Regulators in the US squirm at the thought of water leakage every 10,000 years at Yucca Flats.