I would keep the same pricing formula. Why short-change yourself? You said yourself, it takes the same amount of time or more, so why charge less because the area is small? We as crafters/artists are our worst enemies. We somehow think we are not worthy of charging what we are truly worth. My plumber is going to charge me the same per-hour rate for his services. The painter, the electrician--anyone you hire to do a job is not going to charge you less just because a job is "small". Your machine, supplies, thread and time are worth just as much as any "trade" ( plumber, electrician, etc). Do not be talked into a discount...once you do that, then they will continue to expect a discounted price every time. And they will expect you to to give a discount to every person they send to you.
Good luck, and be strong!