First, my goal is NOT to sell you on the Dillion just because I have one and like it. Just sharing some info, experience and personal opinion. in the end, you have to decide based on the info, your needs and your budget.
note all prices are manufacture list prices from their web site
Rock Chucker Supreme Master Reloading kit. $432.95
This kit provides the following
Rock Chucker
Scale
Hand priming tool
poweder measure
case lube pad
case lube
case neck brushes
case loading block
powder funnel
hex wrench set
debur too
loading manual
Extra stuff still need
primer flip tray
tumbler
case trimmer
case gauge
caliper
shell holder (about $8.00)
Dillion 550B
Everything you need to operate your reloader for 1 caliber not including dies for $406.95
extra stuff needed
case lub
primer flip tray
tumbler
caliper
case gauge
case trimmer
loading manual
scale
Dies. Neither the RCBS kit or the Dillion come with dies
Dillion offers carbide and non carbide dies for 223 and 308
Carbide dies = $ 135.95 for 223
$ 140.95 for 308
Non carbide dies set are $62.95
Redding dies run about $63 for a 3 die set.
I didn’t list prices on things that “don’t matter” as far as progressive vs single stage goes. you need them and they don’t come with either kits.
To me the prices is so very close if you really want the Dillion you are not saving that much (if anything) by going with the Rock Chucker kit. But if you think the Rock Chucker is a better fit for you, you aren’t making a “bad” choice there either.
With practice a single stage can crank out the rounds too. not at the same pace or “effortlessly” as a progressive, but they can produce too. Example, a guy brought his semi auto browning 1919 to the range and was letting people blast away with it. when asked if he reloaded, he said yes and he used a single stage. once he had is process/routine down he was able to produce at a volume he felt was acceptable.
I hope this helps.