Pricing a SaaS Service is not very different from anything other Software Pricing Strategy. While you want to keep renewal friction at a minimum, all other "rules" of pricing psychology still apply.
While most companies out there have intuitively embraced the 'rule of 3', I often encounter teams who don't really know where this rule came from, and have not completely optimized for it.
You need a Hero (what you want people to buy, the word comes from your offer for your "Hero" customer), a Decoy (the house that the realtor shows you to make the house that she wants you to buy look better) and the Anchor (the house that's above your budget, and makes the Hero look cheap.
Looking at most SaaS Model Pricing Strategies out there, I see a lot of threesomes. I'm not sure though if the Anchor and Decoy price points are always really designed for their purpose. Remember, you don't want people to buy your Decoy, and you don't count on them buying your Anchor.