MacroFab. You can get just one from them, and they have real good quality. Only had an issue with them once, and they quickly resolved it and sent me new boards. They *CAN DO* assembly, as well, in case you just are too lazy (like me).

Though honestly, OSHPark is NOT expensive. As long as you like purple? They're one of the better-priced manufacturers out there. Except for the fact you have to buy three.

As far as I recall (I can be wrong now, as it's been a while since I've used OSHPark) it's be $15 for three - since you're getting 3 boards.
And again, that's not a bad price. PCBs are NOT cheap, unless you get them in bulk.

I guess it depends on what your end-goal is. Usually in pricing a board, you should also take your time spent into it. I'm not an expert by far, but I've done a lot of my own personal projects. Usually if there's an alternative that does what I need, I won't waste my time trying to make something similar. If there's a lack of an alternative, I will work on my own. (For example, one of my projects I'm playing with is for the P-Roc system, to hook up to one of the RGB LED driver boards, that will allow an RGB flasher. I've been looking and hadn't seen anything capable to do that yet.)

Modifying my answer, since apparently I wasn't aware..

No more on Macrofab. They terminated their small-quantity prototyping. Sadly, now, you're ordering a full panel, so prices are in the upper $600's as of this writing.

Really saddened by this move, will need to check other recommendations here for small, populated boards.