Scarlet Monastery is counted as ONE instance, whether you run one wing or all four. If you run Cath and Armory, taking time to loot after the run, you can usually avoid the lockout.

As Gurblash pointed out, buying all the training, spells, and mounts for your toons when they hit 60 will cost more than a couple coppers. And the cloth and vendored items will help to offset that.