Did i buy the product "as is"? If it is an open source product then i agree with you, the product is provided as is. However, in my mind this is not the case with a commerical products.
When I buy something, whether it is software, a car or a a washing machine i have a contract that outlines what i am buying. If the product contains bugs/manufacturing defects/etc. then i expect the manufacturer to either fix those or refund me. In many countries this might even be legally required (Look for Gewährleistung/Produkthaftung in German speaking countries).
I am not asking for features. I am not asking you to make the product better than what I bought. I discovered a defect that was caused by the manufacturer, not obvious at the time of purchase and as such the product does not match what i ordered from the manufacturer. I am asking you to provide to me exactly on what we agreed upon in our contract. If a developer cannot handle that and wants to distribute their software "as is" that's fine, but that will result in my willingness to pay being lower.
If I buy a product I expect that product to perform as was promised. If it does not and the manufacturer refuses to work with me then it's a breach or contract.