I think - and I could be wrong - that the trees, bushes, and buildings that get generated from the terrain tile sets, while objects, are not counted. Support for this assertion: terrains are 256x256 miles (10 x 10 grid), or 65,536 square miles. If only 50,000 objects are allowed, and that included the trees and buildings from the tile sets, then less than 1 object per square mile would be allowed.
Also, towns and bases have hundreds of objects, and the towns and bases themselves are objects. If each town/base has 250 objects (hangars, guns, bunkers, buildings, etc), and your average map has 140-ish bases and strats, that's 35,000 objects right there.
The exception is trees and other shapes that you drop manually into the terrain from the TE. Those are objects, and they get counted in the budget.