It’s up to you. The Sellermania feed manager allows you to establish the rules you want: to have the same price as on your Prestashop, more or less expensive by x €, y%. You can also set a price for one marketplace and another price for another marketplace.
Sellermania also has the ability to boost your selling prices according to marketplace competition. For example, you sell such and such a product for € 15 on your site, and you define that this same product will be salable between € 16 and € 25 on marketplaces. Sellermania will then position the product at the best price on the marketplaces in the range you have defined.
You can also make promotions on your site but not on marketplaces, or vice versa.
The flexibility is total.