They're relatively expensive (in my opinion). Because the 4 series coupe is built on the 3 series platform, it's built in far larger numbers - meaning that discounts tend to be better on the 4 than for the 2 coupe.

So for virtually the same price, you can get a better equipped larger car.

Although I do have to admit, BMW seem to be going into market fragmentation to a ridiculous level.

The 3 series is a saloon, estate or GT (5 door hatch). Then you have the 4 series, which is a 3 series with 3 doors as coupe of convertible.

Then the 4 series 'gran coupe' which is a 4 door version of the coupe, which was a 3 door version of the 4 door saloon.

Confused yet ?

My brother in law has the original car - a 1 series coupe.

They don't sell because they are too compromised. The original 1 series was tight in the back, remove two doors, add a sloping rear and the back seats are virtually unuseable.

If you want a two seater BMW a Z4 makes more sense.

A 4 series does have rear seats you have a hope of using occasionally.

"none of which seem to have any bearing on engine size." - Mercedes-Benz aren't much better in this respect - They have nearlyas many letter combinations as international airports and their model "numbers" have long been irrelevant to engine size.
Bringback the Standard Motor Company and its one model policy, say I!