Rules Bit (GURPS): A Better Cost for ST and HP is an old but relatively popular piece that places ST on an ever-decreasing logarithmic cost progression (the brainchild of D. Weber). A replacement for existing schemes to reduce the cost of high ST, it drastically reduces the cost to build a mountain-cracking jotun or bus-hurling super β and can even make designing such beings easier.
I’ve heard nice things over the years from GMs who have put his to use. Give the newly polished old article a read, grab its prettier new Tables, and see whether its cost progression works better for the supes in your games.