well, per the official 5e guidelines, going 1v1 against a great dragon is worth what, 6k nuyen or something like that?
the comparatively low risks involved in ritual magic should mean that highly skilled characters with extremely rare skillsets will basically do almost anything that doesn't have a high chance of severe physical drain for 5 bucks (USD, not nuyen) plus medical expenses. considering you can use reagents to reduce ritual drain, it's cheaper to pay for those than to pay for even a trip to a massage therapist to relieve their sore muscles after taking any drain at all, so... spend lots of money on reagents, and you can have a highly skilled magician do your bidding for a mere pittance, i figure

(note: if you're not crazy enough to use the official guidelines, this amount may not be valid).