They have a second or third account which they leave in Egypt forever.
Thus they have a very quick gameplay to make videos.
I myself didn’t make videos but stayed in Egypt way after level 200.
You can imagine how strong a camp can become when you use all available equipment from events and shop events. Strong in comparison to the low tile costs.
It got boring though, and so I moved on.
You can stay in Egypt, if you avoid crucial story mines at the end and only play events and shop events. But then the advantages of higher regions, like stronger equipment, are not accessible to you.
For every segmented event you can check the tile costs for each region on the wiki, like here
Scroll a bit down and choose Egypt.
Then compare to a higher region.
So to summarize: Tile costs depend on the region you are in, not on your level.