Slack vs Teams cost is the question behind a lot of quiet collaboration overspend. The two tools do broadly the same job, team messaging, channels, calls, and app integrations, and the organizations comparing them usually run both. That is the heart of the issue. If Microsoft Teams is already bundled into your Microsoft 365 licenses, a separate Slack contract is often a second payment for a capability you already own.
We compare this from the buyer side, with no vendor or reseller relationship and no commission, paid only by the buyer, so the conclusion is about your budget rather than a preferred platform. This page sits in the collaboration and video tool cost cluster and links up into digital workplace cost optimization, where the bundled stack is optimized as one.
How Slack and Teams are priced
Slack is sold as a standalone product on paid per user tiers, billed per active user per month, with higher tiers adding compliance, administration, and unlimited integrations. Microsoft Teams is included in most Microsoft 365 business and enterprise plans at no separate line item, which means many organizations are already paying for it as part of a license they hold for email and Office. As of 2025, Slack paid tiers were priced per user per month on monthly or annual billing, while Teams arrived bundled in Microsoft 365. Confirm current pricing on each vendor page before modeling.
Source: Slack and Microsoft 365 plan pricing, respective vendors, as of 2025. Confirm current figures before acting.
Where the overlap creates duplicate spend
The duplicate cost is structural, not occasional. When Teams is bundled into Microsoft 365 and Slack is bought separately, you are paying twice for team messaging across the population that has both. The Slack contract is the visible, removable cost. The Teams capability is already sunk into the Microsoft 365 license you are not going to drop. So the real financial question is not which tool is cheaper in the abstract, it is whether the separate Slack spend buys you enough that you cannot get from the platform you already own.
When Slack is worth keeping
Sometimes it is. Slack has a strong integration ecosystem and a workflow culture that some engineering and product organizations genuinely rely on, and a forced migration that breaks established habits can cost more in disruption than the license saves. External collaboration patterns and specific third party integrations can also tip the balance. The honest answer is that Slack is worth keeping where it does real work that Teams does not do for your people, and worth cutting where it is simply the messaging tool a few teams prefer while everyone else lives in Teams anyway.
How to decide which to standardize on
Decide on evidence, not preference. Pull active usage for both tools, segment by team, and look at where the real work happens. Three patterns tend to emerge. A clear majority already lives in Teams and Slack is a pocket, which points to consolidating onto Teams. Slack carries critical integrated workflows that Teams cannot replicate cheaply, which points to keeping Slack for those teams and removing the redundant overlap elsewhere. Or usage is genuinely split, which calls for a deliberate standardization decision rather than paying for both indefinitely. The wider method sits in consolidating video conferencing tools.
Migrate carefully if you consolidate
If the decision is to standardize on Teams and retire Slack, do it as a managed migration, not an overnight switch off. Export the channels and history that matter, recreate the critical integrations, move teams in waves, and communicate before each wave. A clumsy cut generates a wave of tickets and resentment that makes the saving feel like a cost. A careful one is barely noticed. The saving is only real if adoption survives it, which is the same principle that governs every rationalization in the collaboration rationalization service.
The bottom line on Slack vs Teams cost
If you already own Teams in Microsoft 365, treat Slack as a cost that must justify itself, not as a default. Where Slack does real, irreplaceable work, keep it for those teams. Where it is duplicate messaging, consolidate onto what you already own. Either way, the saving comes from removing the overlap, not from a tool preference.