Phil,
It would always depend on the studio and the budget. A multi instrumentalist (one person doing more than one track) will usually program the drums first. This would often be samples of live drums. Then they would add acoustic guitar, bass, electric guitars, keyboards, vocals, background vocals, mix.
it usually takes about an hour per instrument. An hour for vocals. An hour or more to mix. This usually takes longer because one person is doing it.
On sessions like I do are live drums, bass, rhythmn guitar keyboards, usually piano. Then overdubs on guitars, any keyboards, strings, etc. would be done at the same time depending on the budget. You factor in about $75 for any extra musicians, dobro, bango, fiddle, guitars, whatever. Then lead vocals and background vocals. Mix.
Takes about twenty minutes for the tracks, thirty minutes for overdubs, and hour for vocals. And hour to mix.
For me there is nothing like three-four guys playing at the same time. They are thinking about their parts and how it works within the song. Solo guys tend to lose context sometime and it gets mechanical for me. But you work what you do. Sometimes it is about the same amount of money and of course you have the time factor involved. If someone like yourself just had a couple of days in town, it would be worth the $50-$75 extra to get it done in one gulp.
Almost nothing is going to be done on a "pre-recorded drum loop." Those are the real cheap studios that make the song conform to their drum tracks. I have no use for that.
MAB