...looking at the title of this thread, why would anyone compare anything on radios that cost 1-3/4 times more (FTDX-10), or 3-1/2 times more (FTDX-101), with a radio like the 7300? Like you said, they better be better...
Because oftentimes, it costs a manufacturer no more to offer better performance. It's unforgivable for a manufacturer to release a product that's prone to high levels of hiss and distortion.
When I see someone reply on this topic with "but you're comparing transceivers in different price classes," it tells me they know little about circuit theory. If I can economically design my own low-noise, low-distortion headphone amplifiers, why can't the manufacturers?
The same is true with the IC-7300's mechanical relays. The videos you see of N4LQ's amplifier key line modification is my design. It would cost Icom no more to replicate the keying scheme used in the IC-7610. Only the gullible and uninformed believe that you always get what you pay for.
Paul, W9AC
Paul,
Looking at your qrz.com page, I applaud your extreme electronics/technological knowledge. Far be it for me to question you in that regard. Compared to you, yes, I know little about circuit theory, not ever having a vocation in that field. The majority of hams don't have your professional acumen.
But now you're treading into my line of expertise..."Merchandising". Manufacturers have a profit motive, offering a line of step-up products with more advanced features, purposely designed to entice consumers to purchase more top-of-the-line offerings. Why on earth would Icom, besides a second receiver for $2,000 more, put the same performance, features, and specs in the 7300 that they do in the 7610? If you don't need a second receiver (and many really don't), they'd be cannibalizing their upper-tier product. Despite the fact that it doesn't cost them any more to put the same circuits in the 7300. You're looking at this from a cost/designer's perspective. Manufacturers look at it from a revenue and profit perspective. Two different animals.
It's up to the customer to decide what's important to them, and how they spend their money. Manufacturers only provide the products to give them a choice. You want quieter relays and fans?...buy the 7610. Less "hiss" in your headphones?...buy the 7610. The customer is happy, the manufacturer makes more money. That's the way of the world, my friend.
As far as "hiss and distortion" in the 7300, owning two of them I have no idea what they're talking about. In my 61 years as a ham, mostly an admitted "appliance operator" in DXing and contesting, the 7300's meet my needs, and exceed many of the other more expensive and feature-laden radios I've owned in the past. Others may disagree, and that's OK...I don't care.
Calling people "gullible and uninformed" isn't your decision. Let them buy what they want...it's their money

.
Bob K7JQ