All-in-one suites run two meters
A suite that covers marketing, sales and service usually charges for seats and for the size of your contact database. Those two meters move independently. Hiring raises one, a successful lead magnet raises the other, and a small team with a large list can end up paying more than a large team with a small one.
Model both curves before choosing a tier
Write your headcount today and in eighteen months, and your contact count today and in eighteen months. Place both on the tier ladder. Buyers routinely choose a tier against today's database and cross a boundary within two quarters, which is the least convenient moment to renegotiate.