DataRobot
Yes, both Gliffy and Mermaid Chart offer a Free Trial.
Gliffy is designed for Large Enterprises, Medium Business and Small Business.
Mermaid Chart is designed for and undefined.
Pricing for Gliffy Starts at $8/Month when Billed Yearly whereas for Mermaid Chart Starts at $80.00per user / year when Billed Yearly.
Some top alternatives to Gliffy includes Miro, FigJam, SmartDraw, Cacoo, Microsoft Visio, DrakonHub, Creately, Lucidchart, EDraw Max, DrawSQL, Quick Diagram and diagrams.net.
Some top alternatives to Mermaid Chart includes and undefined.