What exactly are you trying to imply with a reference to size and price?
Screws are almost always used when cutting forces are low, or clearance is a potential issue.
Size is based on the intended use case. For example small inserts are generally used for finish turning or boring. You don't need a big honking insert (waste of money )if you are only going to be removing a few thousands.
Price comes down to who makes them, what they are coated with (if anything), and profit margin. For example there aren't cheap inserts, even though they use a screw, and are small.
www.carbidedepot.com
https://www.carbidedepot.com/Inserts/T-TRIANGLE/TCGT/KENNAMETAL-HP-CHIPBREAKER/TCGT21505HP-KC5010
These aren't cheap holders, even though the are designed for small TCMT/TCGT inserts.
www.carbidedepot.com
www.carbidedepot.com
See if you can get your hands on one of these sets from Glanze.
Glanze 10 mm Shank Set of TCMT Lathe Tools Glanze from Chronos, with Free UK delivery and great worldwide delivery rates. Chronos Engineering tools.
www.glanze.co.uk
Glanze 3/8 Shank Set of TCMT Lathe Tools from Chronos Engineering Supplies. Free UK delivery and great worldwide rates.
www.chronos.ltd.uk
I have 2 sets of the 1/2" shank CCMT/CCGT versions and they have been going strong for over a decade and a half.
Shars also sells sets, but i don't know how good the quality is.
Shop Shars Tool today and experience our high quality turning toolholders at a great value, same-day shipping and devoted customer support.
www.shars.com