These are built-in features of a theme. If you want to remove them from your entire store, we need to do some manual developer customization. Generally, it requires ~1 hour of custom development. We do charge $40 hourly.
If you have a complex theme, the custom development may take more time and may cost more based on the complexity. We always send an estimated time before starting changes in such cases.
If you want us to make the changes for you, please send us an email to email@example.com with the subject Remove strikethrough prices and include your store URL in the email. Also please be specific whether you want to remove them for all of your customers or only the wholesale customers. Also, please make sure that we have access to your store admin.
Please note, it is not possible to remove strikethrough prices from a checkout page and invoice emails since these are handled by Shopify.