If you don’t care about the iron sights, the CASM is the cheapest option that is “acceptable” and the cheapest on the list at $180.
The next cheapest option at $199 USD (and the one I personally use) is a Basset Machine mount. Easy on, easy off, holds zero after instal, uninstall, reinstall. I prefer to use irons, but do use an optic when testing loads or ammo.... or I should say I “used to” before May 1st.
The next option is the ARMS 18 at $300. A solid option, they’ve been around forever, and have been the standard to which all other M14/M1A mounts have been benchmarked against for decades.... but if you want the ability to remove your optic to use the irons, then QD style rings are another thing to add to your shopping list.
The Sadlak is a solid option, and a must if your receiver is slightly “askew” as it has some built in adjustability. Not my favourite, and the most expensive option on this list.
Cheers!