JLCPCB has a very cheap SMT service that will solder most of the parts for you; the limitation is that it can only solder components in its "part library" which consists of only about 700 commonly used parts, such as 0603/ 0402/0805 resistors/capacitors as well as some common transistors and chips. It can only assemble one side. The pricing is $8 base cost plus $0.0016 per smd pad. (
http://www.sz-jlc.com/home/vorderadd.html)
I'm not sure if they will ship outside of china though, as the online system for submitting pcba orders is in chinese only. Everything is done through their online system which parses your BOM and xy file, matches your parts against their parts library, and shows you a preview before submitting the order. I've used this before and you can submit a pcba order without exchanging a single word with a human.