I don't think EKs email upgrade offers give much, if any, value at all.

I fly from Asia to the UK via DXB and an economy return is usually ~£600 whereas a business return is ~£2100. I usually get emailed upgrade offers to J for £3-400 per leg (remember, there are 4 legs in that journey) so it essentially works out at the same price. So if I'm flying EK, I either book business to begin with or book economy and don't upgrade. On my last flight I actually did upgrade from Y to J on one leg and there were approx. 10 people in the J cabin whereas Y was full. It did make me wonder why they don't offer the upgrade at a lower price presuming many more people would take it.

Contrast this to AY, where you can get the economy return for £600, and then upgrade the longer leg (HEL-wherever) for £3-400 (if available, which it usually has been) giving you a total cost of < £1400 return compared to their actual sale price of business being ~£2100. Of course, AY product is substantially inferior to EK but their upgrade pricing makes more sense to me.