I was wondering the same!
If someone is paying you 300k and you are not a Director, get out and start your business. You are being exploited for your talents that is if you are in that position on merit.

This is the salary of county ministers. Unfortunately most of them are not in those jobs on merit

I know many software devs in Nairobi earning 300-700k per month. Network engineers earn much more. But I doubt they are ready to start a business and nurture it.

Businesses need much more than talent.

Yes, you need capital and connections but skills are key as I'm sure you already know what the market needs. You don't have to compete with your employer, I can tell you from experience it won't work.
For example, I know of an editor from one of the leading TV stations, he has an editing company on the side that does editing for weddings and events, popular Videographers use him to do the editing and I can tell you he makes more than his job. He has now employed people to do the job while he works for easy money from his employer where he gets over 250k. But it's taken time to build. He also has a guy who edits music videos and that business is booming. Now, such a person will never be under the mercy of the employer... and that's where we should all aim at... Believe it or not, it opens doors for you, your employer could even subcontract you for a larger fee. Only the fear of losing our comfort zone keeps us down, that and of course trying to survive earning good money in jobs we're not qualified for.

Very possible. I have hired developer in India in the past, I paid them $3500 for work that I knew took them less than 50hrs. You just need about 1 of such project in a month to make Ksh.300k.