The Reaper and LOTR miniatures (A knight, human male footsoldier and female archer) measured about 34-36mm excluding base and helms.
I measured the German soldier that is part of my recent Matchbox build and he stands at 22mm high.
As a comparison, I measured a WH40K Terminator which comes in at 45mm excluding base. However those blokes are in Terminator armour and the average Space Marine is 7-8' tall gaming universe wise.
As I mentioned in an earlier post; Modern 25mm miniatures tend to be around 28mm min. now, the so called "Heroic Size". Certainly in the WH40K range, even the vehicles and accessories are closer to 1:48 than 1:72/76, in keeping with the figure heights.
I always caution comparing gamining miniatures with scale model sizes, the comparisons are not as simple as first thought.
I am certainly not poking holes in your logic, just explaining how the miniatures world tends to work.
Cheers
Mike