Hi honje... Maybe that is a naive way of thinking about it. Firstly your question implies that all EA that are profitable consistently or for a period long enough to make use of some edge to make a profit are to be sold by sellers... It is really hard to gauge what "Price" to put on an EA like that.. since someone can trade it with a large sum of funds and profit a similar % as EA developer, yet have a much larger end amount eg. 10% of 10,000 vs 10% of 10,000,000 ..... gives 1,000 and 1,000,000....
It also takes some skill and dare I say it...sometimes a little bit of luck to determine when an EA shifts from positive expectancy to negative... So say for example an EA would provide a 100% gain, but eventually starts to under perform and lose 50%... leaving 50%... The EA developer may only have 100,000 to put on the EA and thus will make 50,000 before taxes .etc... vs if they also sold 10 copies at 5,000 each... making an extra 50,000.... while getting 50,000 in the same time...
Ea developer has to then work towards a new edge in an EA...since the last one no longer can be used...
So to answer your question, No.. seller of EA's may not be the richest people in the world... if they are honest and legitimate... and some may even have enough funding to run their EA's without having to sell.... Like with any industry, there are 'bad apples' and those just keen to exploit others far less knowledgeable... they use tricks to make the EA look better or deception hiding a longer-term negative expectancy EA in a short term profitable one... or even how they did testing to fool the buyers....
Final point is, nothing is stopping you from making a legitimate EA that you can sell for a similar price as you show in the image....other than yourself.... but do you have the patience, commitment, drive,..etc... to follow such a path to build the required skills... knowing that there may be a chance you can fail... then recover from the failures and continue on...