You need to compare the overall total in quotes with other quotes, not get comments on individual items from people who are not doing the work and know nothing of local market rates, and don't know the builder's own costs or overheads.
All contractors will price items differently and will have various individual items cheaper or more expensive than others.
The fundamental issue is to ensure you are comparing like for like quotes ie all builders are quoting for the exact same thing, so that the only difference is the price.