If BMW had had an SWB version in its portfolio, the sales numbers — especially in Europe — would have been significantly higher.
The sales number would be significantly higher if it was cheaper, not if it was smaller.
I call BS on this claim.
So..
Based on UK registration data (because it's the only place I know to get model breakdowns), it's possible to get an idea of the split between SWB and LWB.
With limited data for the F01/02 generation, the split SWB:LWB was 57:43%. The best selling model (based on limited data) was the 730 diesel, the mix between the 730d and 730Ld was 70:30.
For the G11/12 generation, the average split was 56:44%.
Overwhelmingly, the best selling model was again the 730 diesel. The split here was 81:19 in favour of the SWB. For reference the 730d did 4204 units, the 740d did 1382 units, the best selling LWB model was the 730Ld which did 1011 units.
The 40e/45e/40i cars were all >50% LWB versions... they just didn't do anything like the number of units as the bread and butter 30d.
The 40d was 60:40 SWB.
750 were all SWB, 760 were all LWB, but they're a small fraction of total sales.
Conclusion, this is only the UK market, but as the second largest car market in Europe, I think it's probably representitive of the EU too. The split between Long and Standard wheel base can be generalised as 55:45.... so call it half of 7-ers here are SWB. The cheaper engine versions skew hard towards SWB, the bigger engines skew towards LWB - this is pretty intuitive IMHO. Not having the cheaper entry versions goes hand in hand with not having SWB vehicles. This was HALF the 7-er customer base here.
Also, G70 related side note, i7 seems to be selling 2:1 compared to the ICE/PHEV 7-ers. In the same way that the diesel models were most popular in previous models, the i7 is likely more popular because these are incentivised through reduced taxation.
The USA and China are obviously different cases... I mean, China gets a Maybach with a six cylinder.. so <shrug emoji>