The caliber changes on the 550b are more expensive than the Pro2000
Powder funnel $11
Powder die $15
That's $83 vs $55, which probably reflects the addition of the powder die (which allows quickly changing the powder measure between toolheads without readjusting the die each time.)
With the Dillon press, you don't buy an expander die, as this is done with a caliber-specific "powder through expander" funnel. So, I suppose you could subtract the $11 powder funnel.
The apples vs. oranges part comes into play with the powder measure. With separate expander dies, the powder measure just throws powder and can stay put. With the powder-through expander design, you have to install the powder measure on that die.
You don't have to buy an extra powder die per toolhead. That just makes the caliber change faster. So, if you don't mind moving and readjusting the powder measure (including bell), you can save a few bucks.
In terms of caliber change being a pain, I will agree that is true if it involves reconfiguring the primer feed mechanism. As long as you don't have to change that, caliber change takes less than a minute. With primer feed reconfiguration, it can take 10 minutes.
Some Dillon enthusiasts buy a second 550b (or whatever model they have), just so they don't have to mess with changing the primer feed!
I can't say that's crazy, because all the calibers I reload use large primers, so I keep my small primer parts in a box...
But I will confess to solving the problem of readjusting the powder measures by installing one on each of the 4 toolheads.
IMO, any of the presses from the "big names" are quality machines, with good factory support. Very few reloaders (me included) own more than one brand, as they represent a sizable investment, so I'm not sure how the "color wars" really get much traction.
Probably like Ford vs. Chevy...the one you own is the best truck made, period. Why? Well, because it's the one you bought...