I can not comment on how many are out or why they were pulled because I don't know.
But: this can not be the reason.
You say.
"Secondly, they are getting killed on their 25¢ chips because of their cost."

If the MGM bought the casino equipment from Paul-Son, tables, chairs, etc then the chips were probably free. Replacement cost would be 75¢ or maybe a little less. 50¢ loss on a 25¢ chip would be nothing compared to the profit on the $5, $25, and $100. Average it out!

The chips were pulled for a reason but not cost.