The cheapest quote is rarely the cheapest job. The gap between quotes usually isn't margin. It's scope. Reading a quote well means comparing what's actually included, not just the total at the bottom.
Fixed price versus estimate
A fixed-price quote commits the tradesperson to a number for a defined scope. An estimate is their best guess and can move. Neither is wrong, but you need to know which one you're holding, because they're not comparable on price alone.
Read the exclusions
The most important part of a quote is often what it leaves out, such as consent fees, disposal, making good, or materials priced separately. Two quotes can look far apart until you line up their exclusions and find they've simply drawn the boundary in different places.
Variations
Ask how changes are handled before work starts. A clear variation process, one where changes are described, priced and approved in writing before the work happens, is the single best protection against a surprise final invoice.