The phrase 'varies extremely' is correct and usable in written English.
You can use it to refer to a wide range of differences or changes in something. For example, "The cost of tuition at different colleges varies extremely."
The reported prevalence of thrombophilia in children with VTE varies extremely between 10%and78%8% in different registries.
It indicates that the viscosity of NEWMS varies extremely depending on the silica concentration.
The results of this study also show that, despite using the same medium, transformation frequency varies extremely (maximum ∼106 times the difference) according to the strain and plasmid combinations and the presence of the putative promoting pheromone.
The incidence of biliary tract cancer (BTC) varies extremely in different geographical regions.
However, the GISCi survey found that the proportion of treated CIN1 lesions varies extremely between different centres [ 12].
Although tranexamic acid (TA) has been effective in reducing bleeding after cardiac surgery, the TA dosing scheme varies extremely and the agent is highly overdosed in most relevant trials.
Cost-optimal designs turned out to vary extremely depending on the prevailing conditions concerning contaminant concentrations, branching ratios, and unit costs of both reactor materials.
Calculated shoulder joint loads vary extremely among different authors [Anglin C, Wyss UP, Pichora DR. Glenohumeral contact forces. Proc Inst Mech Eng [H] 2000 214 637 44].
For example, the fertility rates in the different districts that make up India vary extremely widely, from almost 5 (roughly, five children per couple) in some districts to less than 1.7 in some others.
The methods used to hookup GIS and simulation models are also vary extremely from one application to another (Wilson and Gallant 2000).
The surface pH of the paper did not vary extremely, the neutral papers having pH around 5.7, close to that of CO2-saturated deionized water, while the acidified papers had a pH range 4.2 4.5, and the pH of alkaline papers ranged 7.2 7.6.
