Spellchecking by humans is more expensive and not instant. Grammarly is something between the classic software spell checkers and professional human spellcheckers.
Producing well-written documents is essential if you want to appear competent and professional. Using tools is helpful, especially when you are not a native speaker.
Turn employees from noticeably not able to pull off the job to sort of pulling it off.
They have annual subscriptions that get sharply discounted on a regular basis, where it comes out closer to $70 a year. I pay for that, since I usually do need the editing help, but the linked article certainly gives me pause.
Enterprise. That’s a cost that just doesn’t matter.