They are crooks and any online water treatment dealer, plumbers are a bad choice, can sell you any type you need for $80-$130 per cubic foot bag. You may only need 1 to 1.5 cuft. Local dealers will be only a bit more.
And if you have the desire and can use basic hand tools you can replace your own resin.
You also need a new distributor tube and bottom bracket, yours probably has broken and is allowing resin out of the tank. If you take yours in to a local dealer they should be able to duplicate it for $10-$20. The only other possibility is a bad distributor tube oring that's up it the bottom of the control valve.
Otherwise you could buy a new softener online for between $600 and $800 depending on the size you need, and install it your self or have a plumber do it for $250-400.