Module has different configurations that can increase/decrease your website prices during eBay publication.
– Price surcharge (on categories / manufacturers / suppliers)
– Price override in “Fastbay” tab inside a single product sheet
– Price with taxes (YES / NO) – Configurable in the general module configuration
– Specific prices  – Configurable in the general module configuration
If after these checks you still find a different price, check that the “exchange rate” for the default currency used in your site (eg. EUR)
matches “1” in the Localization -> Currencies menu of your site.
Otherwise, update it to the correct value and try again with a new synchronization.