A report on the Estimated Costs of the 2018 IRC Code Changes by Home Innovation Research Labs has determined the cost impact for most homes ranges from a minor $100 increase to a $600 savings over the 2015 International Residential Code. These typical values will vary based on the climate zone and house configuration. See the full 2018 IRC Cost Study
This is a summary of cost impact ranges for code changes that are expected to affect typical construction in most climate zones.
There are a number of code changes that would not apply to a typical home or location: for example, homes constructed in high seismic design categories, flood zones or homes with decks. The second chart itemizes the cost impact for code changes that affect construction costs for these non-typical features.