I have an RCBS Pro2000. It came with both small and large primer seaters and one die plate but no shell plate. Also it came with a press-mounted (no die required) powder-drop assembly with a micrometer adjustment and inserts for pistol/rifle/big rifle).
Shell plates are $31 and die plates are $19 (MidwayUSA pricing). So that's it for cost. Assuming you want to keep your dies mounted and adjusted, and assuming none of your shellplates do "double duty" it will cost you $50 per caliber.
Changing calibers can be done in less than 2-3 minutes, and I'm not talking moving like a NASCAR pit crew or anything. Everything is really easy to get to and the whole thing requires 3 allen wrenches, which are included with the press. Although if you are changing primer sizes then you will need a regular 7/16 wrench but I think everybody has one of those
Adjusting the powder drop is as simple as adjusting the micrometer to the setting you previously wrote down for whatever load you are working with and dropping 3-5 charges to get the powder flow "settled". And of course weighing the final throw as a sanity check.
If you are going from a rifle case to a pistol case you have to take the top half of the powder drop assembly off (it comes off in one piece with one thumbscrew) and swap the rifle insert for the pistol one. Or vice-versa.
So all told, the most time-consuming change (say, large rifle to small pistol) can easily be accomplished in 5 minutes or less. And none of it requires 3 hands or special tools. It is really easy.
Also I would like to point out that if I were thinking about buying multiple presses I would still need the same $31 worth of shell plate per caliber. I'd effectively be trading the expense of a $19 die plate for the expense of a whole 'nother $600 press (and for each caliber!!). In my mind there is no break-even point for any progressive press unless caliber changes are a ROYAL PITA. Like for a Dillon 550