I'm an avid astrophotographer, and the prices for cooled mono and cooled color cameras are the same. If you compare a dedicated, cooled astro camera to a consumer DSLR then yes, they are more expensive. But apples to apples they are exactly the same price. Actually, looking live the mono version is a bit cheaper:

https://optcorp.com/products/zwo-asi6200mc-p - color $3999

https://optcorp.com/products/zwo-asi6200mm-p - mono $3799