ICD-10-CM that you need in the US can be obtained from CMS free of charge. CPT is obnoxious, but you can also generally substitute HCPCS from CMS as well at no cost.
Source: work for a medical billing company, have had to deal with this garbage before.
And those prices look reasonable compared to drug database license costs.
And the real killer is meaningful use certification.
The whole field seems engineered to prevent competition.
So while ISO costs are unjustifiable, they’re a pittance compared to other compliance costs that most in the field will encounter.