True cost comparison — not just what the pricing page says
Quick Verdict
Slack saves you 100%
Best for Slack
Team messaging and collaboration hub. Free plan has a 90-day message history limit that forces upgra
Best for Trello
Atlassian's visual Kanban board tool. Free plan is limited by Power-Up restrictions, automation caps
Team messaging and collaboration hub. Free plan has a 90-day message history lim...
Advertised
$0
/month
True Cost
$8
/month (typical)
90-Day Message History Limit
Free plan deletes message access after 90 days. Your team's entire knowledge base disappears quarter...
Per-User Cost at Scale
A 100-person company on Pro pays $875/mo ($10,500/yr). Business+ is $1,250/mo ($15,000/yr). The per-...
Slack Connect External Channels
Connecting with external organizations requires Pro ($8.75/user/mo) minimum. Free plan has no extern...
$7/mo annual
Atlassian's visual Kanban board tool. Free plan is limited by Power-Up restricti...
Advertised
$5
/month
True Cost
$20
/month (typical)
Power-Up Limit on Free
Free plan allows only 1 Power-Up per board. Need Slack + Google Drive + Calendar? That is 3 Power-Up...
Automation Command Caps
Free: 250 command runs/mo. Standard: 1,000. Premium: 6,000. Complex automations burn through limits ...
View Restrictions
Dashboard, Timeline, Calendar, and Map views require Premium at $10/user/mo. Free and Standard only ...
10MB Attachment Limit on Free
Free plan caps file attachments at 10MB per file. Standard allows 250MB. Teams sharing design files,...
Slack advertises $0/mo. Trello advertises $5/mo.
Slack has 3 documented hidden fees. Trello has 4.
Slack confidence: 83%. Trello confidence: 80%.
| Metric | Slack | Trello | Winner |
|---|---|---|---|
| Advertised Price | $0/mo | $5/mo | Slack |
| True Monthly Cost | $8/mo | $20/mo | Slack |
| Hidden Fee Total | +$8/mo | +$15/mo | Slack |
| # Hidden Fees | 3 | 4 | Slack |
| Confidence Score | 83% | 80% | Slack |
| Pricing Tiers | 4 | 4 | — |
| Affiliate Program | No public affiliate program | No public affiliate program | — |
Slack advertises $0/mo and Trello advertises $5/mo. However, when you include hidden fees, Slack has 3 documented hidden fees adding +$8/mo, while Trello has 4 hidden fees adding +$15/mo. Based on true cost, Slack is typically 100% cheaper.
Slack has 3 documented hidden fees: 90-Day Message History Limit, Per-User Cost at Scale, Slack Connect External Channels. These add approximately +$8/mo on top of the $0/mo advertised price.
Trello has 4 documented hidden fees: Power-Up Limit on Free, Automation Command Caps, View Restrictions, 10MB Attachment Limit on Free. These add approximately +$15/mo on top of the $5/mo advertised price.
Choose Slack if: Team messaging and collaboration hub. Free plan has a 90-day message history limit that forces upgra. Choose Trello if: Atlassian's visual Kanban board tool. Free plan is limited by Power-Up restrictions, automation caps. The right choice depends on your team size, usage volume, and which features you need most.
This comparison is based on manual research of official pricing pages, terms of service, and user reports. Slack data has a 83% confidence score and Trello has 80%. Prices were last verified in April 2026. For the most accurate estimate, enter your specific usage in our calculator.
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