I have done research on options in hunting in Cameroon, last two years.
Generally, 30-40k, is average offer.
There was an option of self - guided hunt with an outfitter who unfortunately passed away.
This one was in the level of 20k. (if I remember correctly)
Self guided, as described then, was meant as hunting without PH, but with local pigmey trackers, and outfitter provides logistics.
I dont know, if anybody offers such things today.
In the meantime, security situation in Cameroon declined, so you will have to make more careful research.
I was surprised to learn that self guided hunts in few countries are still possible, it derives from french hunting tradition, and can still be found, in french speaking African countries.
However I dont think it is for everybody, a hunter should know his way around, know the language, know the country, know the people, and know how to handle logistics. I think, it is mostly for expats living there.