A used 450 or 550 (in normal times) can be a great way to get into a Dillon at an affordable price.
My first press was a 450, lent to me when the owner shipped out for Germany. When he returned 2 1/2 years later, I returned it to him, and my wife bought me a new 550.
Since then I have bought another 450 and another 550, both used, for around $200 each. Each was missing some pieces, but each ended up fully functional for well below the price of a new one. I turned each over to friends of mine who wanted to start handloading. Both are cranking out thousands of rounds now.
I have seen SDBs for similar prices, but the proprietary dies were a limitation I was unwilling to accept...mostly because I load for multiple calibers. If you only load for one (handgun) round, an SDB at the right price could be attractive.