It's true the lenses Olympus make may take up much less volume than an equivalent large focal length for full frame.
But the downside is they're not cheaper in the prosumer space. The spatial resolution demands put on the lens by a 20MP M43 sensor is actually pretty similar to a 42MP Sony A7Rii. This means the manufacturing tolerances are the same as full frame, which is a large component of lens cost.
This means that for the average consumer not interested in long range wildlife photography where the price of glass does come into play (e.g. 600mm), there isn't any price advantage.
The Tamron actually outperforms the Olympus lens in terms of spatial resolution/sharpness on a 24MP sensor (because the photosites are larger), has a 2 stops faster wide end, and is $500 cheaper.
Even more interesting is that there is only a 14g difference in weight between these two lenses. Granted the Olympus will have better weather sealing.
The average prosumer is going to do the math and see that for a lower total system cost (body + lens) they're getting more in terms of sensor and lens performance for a negligible increase in weight.
This wasn't true in the early days of Sony's FE system, but as of 2020 with modern, sharp, short flange lens designs from 3rd parties - the price/performance ratio has become better than I ever predicted it would be
But the downside is they're not cheaper in the prosumer space. The spatial resolution demands put on the lens by a 20MP M43 sensor is actually pretty similar to a 42MP Sony A7Rii. This means the manufacturing tolerances are the same as full frame, which is a large component of lens cost.
This means that for the average consumer not interested in long range wildlife photography where the price of glass does come into play (e.g. 600mm), there isn't any price advantage.
As an example, have a look at the 12-100mm F4 for Olympus (https://www.bhphotovideo.com/c/product/1281427-REG/olympus_v...) vs the new Tamron 28-200 F2.8-5.6 for Sony FE (https://www.bhphotovideo.com/c/product/1568708-REG/tamron_a0...)
The Tamron actually outperforms the Olympus lens in terms of spatial resolution/sharpness on a 24MP sensor (because the photosites are larger), has a 2 stops faster wide end, and is $500 cheaper.
Even more interesting is that there is only a 14g difference in weight between these two lenses. Granted the Olympus will have better weather sealing.
The average prosumer is going to do the math and see that for a lower total system cost (body + lens) they're getting more in terms of sensor and lens performance for a negligible increase in weight.
This wasn't true in the early days of Sony's FE system, but as of 2020 with modern, sharp, short flange lens designs from 3rd parties - the price/performance ratio has become better than I ever predicted it would be