How efficient can LEDs become?

One of my favorite articles is “Is it worth changing the lightbulb”. The article contains the following table that shows rather clearly that it’s pretty much always worth replacing old incandescent light bulbs by LEDs:

However, even within the category of LEDs there are differences. The EU has given us efficiency labels that place all LEDs I could find in the “E” or “F” tier:

Hence I wondered, what the physical boundaries are.

Most LEDs I see are currently around 110 Lumen/Watt.

The current market

The 806 Lumen / E27 / 2700K / 15,000h lifetime lamps I recently bought need 7 Watt and costed 3.12€.

• Philips Ultra Efficient LED lamp: 210 Lumen per Watt. That is 840 Lumen for 4 Watt (E27 / 3000K / 50,000 h liveftime, 10€). Hence you pay 6.88€ more, but you need only 57% of the energy. It also claims to have a 4.1x the livetime. That means you save roughly 150 kWh. Assuming a price of 0.33 €/kWh that would be 49.50€. However, the lifetime claim is crazy. Assuming it lasts 10 years instead of 50 and that you need it about 3 hours per day in average, that would be 11,000 hours. It would still…