My goodness, assuming that's US quarts, that's over 9 litres.
(Had it been UK quarts, it would have been over 11 litres!).
Quite expensive if we were talking extra virgin olive oil, for example.
What are these beasts of which you speak? I haven't come across them in my sheltered UK existence.
What advantage do they have over sticking the turkey in the oven?
[EDIT: ok, I see now - speed, and probably taste]
I must say, I'd be very reluctant to use a device that forced me to use (on cost grounds) "cheap vegetable oil". I know it's only once a year, but I assume you'd want to use the device on other occasions as well.
Would it be possible to use pre-melted good quality lard (or beef tallow if you can get it, or make it), or even butter? Not sure how much you'd have to melt to make 9 litres worth though.
OK, I see smoke point is an issue, and butter might not cut it (although ghee would, but it's dear). However, lard and beef tallow would.
An article about beef tallow:
I couldn't find any actual oil capacities for the ones I looked at online, but given that you should be able to re-use the oil ( or fat, if used), cost is perhaps less of an issue, and less reason to use dubious cheap oils.
If it's technically able to be used, I'd think home-rendered beef tallow would give an excellent flavour.
Another beef tallow enthusiast. One of the commenters actually renders their tallow in a turkey fryer (an outside one).