Cost is relatively, and can depend on how much outside support you need from others. You can build your own relatively inexpensively:
Lil Terp
https://skunkpharmresearch.com/passive-butane-extractor-and-reclaimer/
Mk III
https://skunkpharmresearch.com/mk-iii-terpenator/
Best Value Vacuum or Terpp Extractors are good resources for already built components or systems, with Terpp Extractors providing the most after market support, if'n you need any hand holding.
On the upper end, are the commercial extraction systems falling in the, "or more" category, which may include turnkey installation and training. Those systems also include all the ASME/IBC/NEC/NFPA certifications by a third party licensed professional engineer, required to operate in a licensed extraction facility. Locally operating an unlicensed extraction operation is a Class B felony.
Good shatter wholesales here locally for about $15/g, or about $425 oz, and retails around $35/g. It must pass lab analysis/certification for content, residual solvents, pesticides, and mold. Licensed dispensaries can't sell any that is not certified.
The reason for the analysis and certification requirement, was the public horror and outrage at the results of random lab analysis showing unregulated concentrates to be rife with solvents, pesticides, and mold, as well as varying considerably as to cannabinoid content.
The black market will always fill any niches created by free market regulation, but at least locally, the point has been made that black market quality control is unreliable, leading us to the biggest reasons that might be so.
Specifically equipment, material resources, and process control.
It requires more expensive equipment than just the extraction system, as well as a reliable source of quality uncontaminated plant material, and close control of the process parameter.
If you covet selling quality material at open market prices, a solid business plan should ostensibly include what it takes to meet those requirements, and unless you are also growing your own, the reliable source of quality uncontaminated plant material can be your biggest challenge.
Not only can a contaminated batch turn out badly, it contaminates the system, including the recovered LPG, requiring dumping and cleaning.