My 3-year-old is a big fan of Just Enough and Not Too Much, a children’s book by Kaethe Zemach.

Simon the Fiddler starts the book with a simple, happy existence. He has a cozy house, a great fiddle, a toy animal or two and a few nice pieces of furniture. Eventually, though, he decides he wants more. At the risk of spoiling the ending of a book meant for toddlers, Simon adds more and more possessions until he’s completely overwhelmed. He ends up throwing a party and giving away all the extra hats, toys and chairs to his friends – going back to simplicity.

He has enough; not too little, not too much. And when you’re looking at marketing automation solutions, you need to be sure you’re thinking like end-of-book Simon.

Look at any marketing automation platform’s pricing page, and you’ll quickly be overwhelmed with features, plans and numbers. Worse yet, comparing different platforms’ prices is never apples-to-apples. What’s standard in one solution is an add-on in another. Subscription escalators vary considerably.

Even the definitions of words like “enterprise” and “professional” can be completely different. This leads to an incredibly common marketing automation mistake: Buying too much, or not enough.

How do you avoid this (rather costly) trap? The key is identifying necessary features and functionality based on your business case, rather than what a particular pricing tier includes.

Don’t assume that just because you’re buying from a market leader, you’re getting a full toolbox; some entry-level plans are borderline bait-and-switch.

What are you actually planning to use your new marketing automation solution for? (“Everything it does” isn’t an answer; you’ll never use every tool in a high-end implementation of HubSpot, Pardot or Marketo.) Is email marketing the linchpin? Tracking the impact of social media and paid digital advertising campaigns? Will you be standing up landing pages in it, or using a different tool? What does the rest of your technology ecosystem look like?

It seems simplistic, but getting a handle on these factors is key to making the right marketing automation pricing decision. If everything you expect to need in the near future is covered in a low- or mid-tier package, you don’t need to waste your money upgrading to the Cadillac. Don’t be overwhelmed or awed by features you’ve never heard of and will likely never use; save the cash, and put it to better use.

Of course, you need to be careful when you’re doing this. We’ve seen many cases where features and functionality that seem elementary aren’t included in a particular plan. It’s common, for instance, for bottom-tier marketing automation subscriptions to not include A/B testing capabilities – something that should be core functionality. Some tools can’t stand up a landing page at any subscription level. Integrations and APIs are sometimes treated as add-ons, rather than the key pieces they really are. Don’t assume that just because you’re buying from a market leader, you’re getting a full toolbox; some entry-level plans are borderline bait-and-switch.

The key is identifying necessary features and functionality based on your business case, rather than what a particular pricing tier includes.

Pay attention, too, to what any marketing automation pricing plan includes, and how escalation happens. Many platforms base their prices on the number of contacts in the system – and the triggers for additional costs are often shockingly low. HubSpot’s Pro plan, for instance, runs $800/month when paid annually. But that only includes 1,000 contacts – a number quickly eclipsed by enterprises and SMBs alike. Each additional 1,000 contacts costs an extra $50 … fast turning that $800 into four figures, even before a $3,000 required onboading fee is taken into account.

When you’re buying marketing automation, remember the lesson of Simon the Fiddler. High-end feature sets are impressive, and it’s easy to overbuy. Don’t. But at the same time, be sure your particular business needs and realities are accounted for; you don’t want to accidentally miss out on necessary functionality. With a little planning, you can settle in the middle – just enough, and not too much.