You can buy a Tikka for $500-$550 and sell off the components for at least $100. They were clearancing some T3 models out around $400 for the whole rifle awhile back. So that would have been a $250-$300 action. You can buy a used full rifle for around $400-$450 anytime. Lots of options. Even if the action ends up costing $450, is that $50 really relevant when the alternatives we're discussing are triple the price?
Or you can shoot it as-is and have a 1/2 MOA gun and stop spending thousands to chase tiny groups that don't matter when you get up from prone.
I shot my stock CTR for a long time. Have buddies with nice barrels on custom actions that don't shoot any better. I finally replaced the CTR stock just because I loved the look and feel of the Manners, and not because I needed to. People who are used to 700s and Savages don't realize that Tikkas don't need everything to be replaced. It's a different mindset.