- Sign up for free or with a credit card, but you'll run into problems (or at the very least friction/complications) if you end up trying to use if you something serious
- Speak to a salesperson and have your CFO sign the company up for a long-term strategic partnership.
The examples that you gave are less clear-cut though. Trello Business is $12.50 per month, and supports Google Apps SSO. Trello Enterprise supports general SSO, and costs $20.83 per month. Slack pricing is $6.67/mo for Standard, and $12.50/mo for Plus with SSO. None of these are costs that should really make or break the profitability of a company; considering that the business is using them to generate revenue or to reduce its expenses, how do they compare to other things like property/facilities expenses and employee salaries/benefits?
Lower tiers of SaaS products are more-or-less strictly designed for:
- individuals or very small businesses where everyone is friends
- who don't have exacting requirements/audit/traceability/reporting concerns
- who are willing to accept some pain/inconvenience if they use it outside of its design parameters
Credential-sharing services in the age of SSO are a dirty workaround designed to circumvent SaaS product segmentation (which would otherwise cause established companies to effectively subsidise tiny startups). I'm all for hacker philosophy, and perhaps this applies less to your situation than it does to the OP, but I do think the idea of credential-sharing is a horrible kludge that has only risen to prominence because of the specific issue that I mentioned, and which only leads to more problems with things like non-repudiation.