Prompt Title: Expensive WordPress models.

Here are 30 of the best and most popular premium WordPress plugins, in no particular order:

1. Gravity Forms - a powerful form builder plugin with advanced features
2. WPForms - another form builder plugin with drag and drop functionality
3. Yoast SEO - a comprehensive SEO plugin for optimizing your website's content
4. Jetpack - an all-in-one plugin with features for site security, performance, and design
5. W3 Total Cache - a caching plugin to improve site speed and performance
6. WP Rocket - a caching plugin with easy setup and optimization features
7. iThemes Security Pro - a security plugin with advanced protection and monitoring features
8. OptinMonster - a lead generation plugin with various form types and targeting options
9. Advanced Custom Fields Pro - a plugin for creating custom fields and meta boxes in WordPress
10. MonsterInsights - a Google Analytics plugin with advanced tracking and reporting features
11. MemberPress - a membership plugin for creating and managing membership sites
12. WPML - a multilingual plugin for creating and managing multilingual WordPress sites
13. WooCommerce - a plugin for creating and managing online stores on WordPress
14. Easy Digital Downloads - a plugin for selling digital products online
15. LearnDash - a plugin for creating and managing online courses
16. AffiliateWP - a plugin for managing and tracking affiliate programs
17. Ninja Forms - a form builder plugin with advanced features and integrations
18. Soliloquy - a responsive slider plugin with various customization options
19. Smush Pro - an image optimization plugin for improving site speed and performance
20. BackupBuddy - a plugin for creating and managing backups of your WordPress site
21. Pretty Links Pro - a link management plugin for creating and tracking branded links
22. Envira Gallery - a plugin for creating responsive galleries and albums in WordPress
23. WP Courseware - a plugin for creating and selling online courses
24. CartFlows Pro - a plugin for creating custom checkout and sales funnels
25. Formidable Forms - a form builder plugin with advanced features and integrations
26. SeedProd - a plugin for creating custom landing pages and coming soon pages
27. UpdraftPlus - a backup and restore plugin with various cloud storage options
28. All in One SEO Pack - another comprehensive SEO plugin for optimizing your website's content
29. Affiliate Royale - a plugin for creating and managing affiliate programs for your products or services
30. Schema Pro - a plugin for adding schema markup to improve search engine visibility and rankings.

Please note that the cost of these plugins can vary depending on the licensing terms and the number of sites the plugin will be used on, among other factors.