buying all live rock vs base rock? Also sump question

[Hightower]

I have had some experience with saltwater years ago, but things have changed. In particular live rock.

My question is this since there seems to be a rule of 1-1.5lbsLR/Gal and that gets bloody expensive.

If you start a new tank that obviously needs to be cycled, but base rock eventually becomes live rock, would it not be more cost effective to do a 50/50 or even a little live rock with live sand and and the rest base rock so that it becomes seeded?

What would be the disadvantages to doing it this way.

I see that the hobby is not cheap, and would like to make costs to have the most value without comprimising quality of life for a reef.

2nd question: I am reading everywhere that there is sump setups but they all have refugiums. Is a refugium absolutly necessary. Can you have a healthy aquarium without it?

Thanks for your time in advance.