There are so many repair service providers providing iPhone screen repairs today, and their prices are all over the map!
It might lead you to think that the more moderate or higher priced repair centres are just greedy!
In the reality of the iPhone sreen repair industry there are different types and qualities of replacement iPhone screens.
Types of Replacement iPhone Screens
New screen made by a manufacturer authorized by Apple (Apple does not manufacture any iPhone hardware components).
A used screen that was removed from someone else's broken iPhone.
Original LCD & flex cables with glass replaced
Original LCD only with third party glass and flex cables replaced
All components of the screen manufactured by third party companies in China (Tianma, Senchao, AUO, LG, Sharp, etc...). The quality of these screens can vary greatly, from being nearly indistinguishable from OEM screens to being very poor quality.
The price charged for iPhone screen replacement typically depends on the type and quality of screens used by any given repair store.
Technical experts are often able to check the quality of a replacement screen by various methods, for example - examing the QR code.
Upon inspection a technician may perceive a third party refurbished screen to present a blurred or unclear QR code. An OEM screen would likely have no defect in the markings.
A deeper inspection of the cables and layers (using microscopes and sensors) can reveal adhesive overflow and irregular edges in the bonding agents used when fusing the layers together. Further the bonding agent in lower quality screens may be brightly coloured.
Normally OEM screens will have a foam pad on the back of the lcd and touchscreen connectors.
None of these comparisons on their own is a sure sign of a low quality screen but these signals combined with a repair providers knowledge of their product source along with how much they've paid for the screens will help them in determining the overall quality of their replacement iPhone screen supply.