Hi Luis and welcome to the forum
Bit of both I would suggest. You should always compare supplier prices with each other, but it never hurts to talk price with them either. Of course it's dropshipping, not wholesale, so you can't nego price based on volume, but what about asking if they offer a loyalty program. If you sell X amount of their products, will they give you an X amount discount and things of that nature.
Nego is part of business, you should never just simply accept anything at face value. Nego doesn't mean you will always get what you want of course, but it does mean that you certainly won't get what you want if you don't at least try!