What makes yours only 220? Is it just a question of purchasing enough runners until you find one that is 280?
Yes.
But the runner makers, of which there are three people who really make runners, might provide the higher hardness sets to larger Nations they have contracts with or who spend more money.
Runners are not just steel, they have a cutting blade for half the length. We balance like a rocking chair on a small few mm part of the runner between the round portion and the cutting knife portion. Too far forward balancing on the round and we skid sideways. Too far backwards on the knife we cut too much ice and go slowly.
Here you see the blade portion:
We have different runners for each ice condition and temperature. Deeper grooves and thinner cutting knives for more control, and wider knives for less control. In the picture you can see the cutting knife, and on each side are cut-out grooves. I personally have about 10 different sets. I use a wide spine and shallow grooves when it's warm (so it doesn't cut too much), etc etc.