Probably, they can't produce instrumental amp due copyright issue.
Since when has that bothered Chinese companies?
That's not really the point, noise is not inherent in the architecture, AD8129 has 4.5 nV/√Hz for instance ... the architecture can target any niche in-amps are targeted at. So if Chinese manufacturers want to build differential to single ended amplifiers without trimming, it's there.
I admit, I'm not familiar with transconductance based differential amplifiers. Do they have high input current noise? The AD8129 has ten times the input current noise, of the AD620, at high frequencies: 1pA/√Hz vs 0.1pA/√Hz at 20kHz and much higher 1/f noise, so at 10Hz, so nearly 20pA/√Hz vs just over 0.2pA/√Hz. I know the AD8129 an RF part and not optimised for low frequency operation like the the AD620, so we're not comparing like with like.
Do you know of a part more suited to the original poster's application?
I know that we should do something,if we do not do something, we are just limiting ourselves to the high tech giants to drink the juice out of our pockets with out dated parts at high costs!
What do you think we need to do?
The semiconductor manufacturers are not ripping us off. Some things, such as low noise, low offset, high CMMR, high accuracy, DC amplifiers are technically difficult to achieve and are costly to make. New technology has made many things cheaper, such as achieving higher speeds, more complex designs on the same piece of silicon, but not everything has progressed at the same rate. Basic laws of physics can often get in the way, which gives us diminishing returns in certain areas such as low noise design.
I've already told you how you can nearly half the cost of your design: replace the AD620 on the right hand side of the drawing with a cheaper, ordinary op-amp.

EDIT: Corrected decimal point on resistor value, in schematic.