How expensive a fusion reactor is depends on which designs end up working. Some of them are actually projected to be pretty cheap, and mass-producible. Helion for example is expecting a cost of two cents/kWh, and uses more advanced fuel with much less neutron radiation. Stellarators on the other hand are quite complicated to build, though some recent work has simplified them significantly.
Activated D-T reactor parts only have to be buried for a few decades and then they're fine.
Long-term fission waste is almost entirely transuranics, formed by heavy atoms absorbing neutrons without fissioning. If we were to use fast reactors or thorium molten salt reactors, then that problem would go away, and we'd be left with just fission products, which are only troublesome for a couple centuries.
Activated D-T reactor parts only have to be buried for a few decades and then they're fine.
Long-term fission waste is almost entirely transuranics, formed by heavy atoms absorbing neutrons without fissioning. If we were to use fast reactors or thorium molten salt reactors, then that problem would go away, and we'd be left with just fission products, which are only troublesome for a couple centuries.