What this involvesWhen lopping is the right move
The useful comparison is not only how much can come off, but whether the tree will still work in the space afterwards.
Lopping sits between pruning and taking the tree out. When a tree has outgrown the block and a light trim will not keep it in check, a heavy controlled cutback may be the practical answer — it clears what needs clearing and brings the height or spread down without removing the tree.
A heavy cutback can produce strong new shoots, so the quoted result needs to account for what is likely to grow back and whether the remaining canopy will still suit the property.