Items listed for sale have included marathon participant jackets and shirts, volunteer jackets, and Boston Marathon finishers medals, ABC News reported.
One eBay user selling his medal, which had a high bid of $266 as of Thursday morning, said he sells his medal every year.
"I hold the memories, but I'm not a momento/souvenier [sic] type person. If I keep it, it ends up in a shoebox so I hope someone will buy it that will find it interesting or even inspiring," the user wrote on the post, adding that he plans to keep $120 of sale to pay for his entry fee for next year's marathon and the rest will go to a "first responders or victims fund."
Another eBay user has listed used participant's souvenir bag for $31, ABC said.
"Also included are wrappers from two protein bars consumed by the runner prior to the race," the item description said.
Non-race-issued memorabilia for sale on eBay includes T-shirts that say "Pray for Boston," "Prayers for Boston," "Boston Strong," "We Remember" and "Never Forget."
No one selling any of the items responded to requests for comments made by ABC News.
In a statement, eBay said: "We are deeply saddened by the Boston tragedy and our thoughts and prayers go out to those affected. Out of respect for victims, eBay does not allow listings that graphically portray, glorify or attempt to profit from human tragedy or suffering. eBay's teams are monitoring related listings to ensure they comply with our policies and also taking into account reports from our community members. When a listing is brought to our attention that may go against our guidelines, we carefully consider the context and all of the details, and decisions to remove items are made on a case-by-case basis. Anyone can report an item to eBay for review by clicking the 'Report Item' link on the listing."