in my experience, building a bike ranges from cheaper than new to more expensive, depending on how you buy/when you buy/where you buy.

My touring bike with an excellent frame from 1990 was built cheaper than new comparable options and with better quality components.

my gravel bike was built up for less than comparable options and with better components.
but it was also built up for more than comparable options.
it's both cheaper and more expensive, depending on what its compared to.

I've built road bikes up for way less than what its cost new, using a used frame.

and I just built a bike up from the tubes earlier this year. That was way more expensive than comparables- both production and handbuilt options.


there is hardly a standard.


as for the OP's bike, it could be set up as an excellent drop bar bike for $500-900 depending on drivetrain, wheels, etc.
almost for sure less than new options from standard retailers and almost for sure with similar/better spec.