In the core Rolemaster product, you will find that every profession has a single cost listed for spell list acquisition (RMC Character Law, page 76 lists these costs for RMC)
For example, the Rogue has a cost of 8 and the Fighter has a cost of 20.
The core rules also say that non-spell user may only learn Open spell lists from their realm and then only to 5th level.
The options to which you are referring (in RoCo III, then expanded in RoCo IV -- similar options exist in RMC Spell Law) expand the levels to which the lists may be learned and the 5x or 3x or whatever refers to the base Spell List Acquisition costs given in the core rules.
For example, the RMC Spell Law has an option that allows non-spell users to learn Closed spells (from first to fifth level) at 2x normal cost (i.e. 16 for a Rogue and 40 for a Fighter) for each level.
Hope that helps...
