Hmmmm, I see. That might be a good alternative, because the per-hour model presents me with a little problem right now...
Assuming that I hired one $15 startup and the work schedule would be the normal 8 hours a day, that'd make: 15 x 8 = $120 a day.
Assuming a normal 5 days a week (with saturday and sunday to rest): 120 x 5 = $600 a week.
A month has about 4 weeks: 600 x 4 = $2400 per month.
Now, assuming a small team that includes 1 animator, 1 artist for things like backgrounds, tilesets and GUI, and 1 composer: 2400 x 3 = $7200 a month for that team.
I'd need over 20 times my current subscriber count on my Patreon to even afford that! So I either pay per asset or look for an alternative way of gathering up the money, such as working for others first (assuming these others even have any money to pay me with).