The question to the source of the money used to buy the bhoga foodstuffs
So a householder devotee should try to earn as honestly as possible and especially try to maintain a very spiritual consciousness at work or business.
Krishna Prasadam is not always purely on the transcendental platform–but rather possibly tinged by the modes, due to the purity of the devotee offering it.
Shrila Bhaktisiddhanta Sarasvati Thakura suggests that people who are materialistically inclined and sahajiyas, or so-called Vaishnavas who take everything very casually, are both visayis, or materialists. Eating food offered by them causes contamination, and as a result of such contamination, even a serious devotee becomes like a materialistic man.
If one cooks oneself and offers and then honors prasadam, it is guaranteed that one will not become contaminated more than what one already is