Hello, 

judging from your comment, you might have forgotten to mark "Included in Price" for the tax, that will be assigned to the sale order of the B2C client. It's assigned by the fiscal position. 

If not included in your system, first, create the "Included in Price"-tax. For example, copy the tax you used before, and change the option in the "Advanced Options"-tab. Than, create the fiscal position that translates the tax-exluded tax (stored as default in your system) to the tax included one. Finally, assign this fiscal position together with the tax-included pricelist to the partner.

I created an odoo app to make this easier and to handle some more cases: \\https://ayudoo.github.io/odoo_business_relationships/

With this module it not necessary anymore to assign the fiscal positions and pricelists manually on contact level. Feedback welcome!

What is "weird"?