Why would someone try to pay you for the gift you are giving them?

Was it your mom?

Lack of self worth (abused neighbor has done this); pride not to receive "charity"; genuine concern the gift's cost will cause economic harm to you; too many gifts given, so a sense of indebtedness develops - I have known folks who do this deliberately so they can leverage illicit "favors", etc etc.

I do that at times when we feel like we deserve it...maybe? It could be many reasons beyond me.

Maybe, they don't want to reject the gift, but suspect the intention of the gift? I dunno.

They clearly do Not like to receive gifts or burden the giver in any way possible.

depends on the gift

call me superstitious but I wont accept a knife or scissors as a gift

... that's baffling. It's not how gifts work.