Other weapons should have weight and the Nyeshk Greatsword should be reduced to 60 weight or something like that.
Mythril Blade: 20p/20m. If you enchant it and it's pristine, that's 43p/20m > 63 power to melee, that's 10 more than a fully enchanted mythril stave (53p/50w) but with no weight in exchange.
Nyeshk Greatsword: 15p/40m/100w. If enchanted and pristine, that's 38p/40m/100w > 78 power to melee but the weight doesn't make it worth it whilst Mythril and Arcanium Blades are weightless.
Mythril Blade: 20p/20m. If you enchant it and it's pristine, that's 43p/20m > 63 power to melee, that's 10 more than a fully enchanted mythril stave (53p/50w) but with no weight in exchange.
Nyeshk Greatsword: 15p/40m/100w. If enchanted and pristine, that's 38p/40m/100w > 78 power to melee but the weight doesn't make it worth it whilst Mythril and Arcanium Blades are weightless.