Why quotes vary so widely
Two fabricators can quote very different amounts for what looks like the same window. Usually nothing dishonest is happening. uPVC windows are assembled from several components that each come in a range of specifications, and a quote is really a bundle of those choices. Knowing what sits inside the number makes it much easier to compare offers fairly.
The useful question is rarely "why is this one more expensive." It is "what is different inside it, and do I need that difference."
The main cost drivers
Profile specification
The frame itself varies in wall thickness, in how many internal chambers it has, and in the quality of the UV stabilisation that keeps it from yellowing in strong sunlight. More chambers generally mean better insulation and a more rigid frame. A thicker outer wall resists warping better in high heat.
Steel reinforcement
uPVC on its own flexes. Most structural sections carry a galvanised steel insert inside the chamber to hold the shape, especially on larger openings and on anything that slides. The thickness of that steel, and whether it is present in every section or only some, is a real difference you cannot see once the window is assembled.
Glass
Glass is often the single largest variable. Single glazing costs least. Double glazing with a sealed air gap costs more and insulates considerably better. Toughened and laminated glass each add cost for safety or acoustic reasons. The thickness of each pane and the width of the gap both matter.
Hardware
Handles, hinges, friction stays, locking points and rollers carry the moving load for the life of the window. Hardware is where cutting cost shows up soonest, because it is the part that moves thousands of times. A sliding window with poor rollers becomes stiff long before the frame shows any age.
Size, shape and opening type
Larger openings need heavier sections and stronger reinforcement. Arched or non rectangular shapes need more fabrication work. A fixed pane costs less than an openable sash of the same size because it needs no hardware.
Mesh, grills and finishes
Mosquito mesh, safety grills, laminated colour finishes and woodgrain foils are all genuine additions rather than standard inclusions. Check whether a quote includes them or assumes you will skip them.
Installation
Removing an old frame, making good the opening, sealing, and finishing are labour, and a quote that looks low may have left some of it out. Ask explicitly what happens to the existing window and who repairs the surrounding wall.
Comparing two quotes properly
- Ask for the profile series or system name, not just "uPVC"
- Ask whether steel reinforcement is in every structural section
- Ask for the glass build, meaning pane thicknesses and the gap, not just "double glazed"
- Ask what the hardware is and what warranty covers it
- Confirm whether mesh, grills, removal of the old frame and finishing are included
- Confirm who is responsible if a measurement is wrong
Once those six answers are on the table, two quotes usually become genuinely comparable, and the cheaper one is sometimes the better one.
Where spending more tends to pay back
Hardware and glass are the two places where the extra cost is most often justified, because hardware determines how the window feels for years and glass determines how it performs. Decorative finishes are the easiest place to economise without regret.