It doesn't look like a full pay option is available. But you could check with them. I don't know what levels of inventory they have to make that possible. I'd consider doing that maybe at the halfway point but for now I'm okay with the subscription plan. It would probably take me the same amount of time anyway so this at least is a little easier on the wallet.
Been looking into it, no pay off early option. Also didn't realize it was closer to $70/mo minimum plus taxes and shipping since they ship 5 sets $15 ea each month. Have been reading some reviews about them running out part way through on other projects which leaves you out hundreds and with an incomplete set. Got me rethinking it.