The big expense for push-to is the computer and the encoders. 8k encoders will work fine but 20k are even better as more accuracy. But the price on large body encoders goes up fast the more tics they have. I have both 8k and 10k ones. Computers can be cheap if you don't want more than say planets and Messier objects as you can get that from a Meade Magellan I or II ,or a JMI NGC-microMAX for maybe $50, but that is only a 245 object database. Price goes up based on processor speed and number of objects in the database. The largest Tangent DSC like the Celestron Advanced Astromaster, Orion Sky Wizard 3, Lumicon Sky Vector 3, and the JMI NGC-MAX will set you back from $100-$150 used. Those are 12,046 object databases. Argo Navis for close to double that price is 29,000 plus (including 1100 you can add yourself).But the AN also has dual processors one specifically for tracking encoder movement so you can move the scope a lot faster and/or use even denser encoders without it losing track. The Nexus DSC is the ultimate doubling the price of the Argo Navis. The Tangent computers are no longer updated (version 3.52 is the last and has been for awhile). Argo Navis has free updates and can be downloaded. Likely same with Nexus.
The Argo Navis head is AUD $359 (about USD $247)
The Nexus DSC head is US $349.95
Though, to be fair, most people get the Nexus with WiFi, cables, & charger for USD $404.95
A power cable ups the Argo Navis to USD$265, but still not WiFi or with a rechargeable battery, so it's fairer to compare it to the lower priced Nexus DSC without WiFi.
Some difference in price, but nowhere near double. And 2.3+ million objects in the database (>73K in flash memory). Nexus is compatible with encoders to one million ticks
and you cannot move it fast enough to confuse its readout.
Having used both, I regard the Nexus to be a more updated head unit, though Argo Navis works just fine.