DNA synthesis companies: cost per base, turn-around time, codon-optimization algorithms
Are you working in academia? It might be worthwhile to call the companies directly and see if there is a discounted rate for your institution (another lab or department may have already set something up). 

You won't be able to get information on the different algorithms if they are proprietary.  However considering that codon usage data is public and shared knowledge, I can't imagine that the different algorithms are that much different. I think there are some tricks for choosing certain codons near the transcription start site in some organisms? From what I hear, the algorithms are constantly changing. I could tell you how my E. coli optimized gene from GenScript worked two years ago, but they'd probably design it differently now. 

Okay - GenScript calls their algorithm "proprietary", so they are not sharing the details. DNA2.0 says their algorithm is patented, so it's out there for inspection. They published a PLOS paper on their E. coli algorithm: Welch et al.. 

Although, maybe all they do these days is spit out codon sequence randomly:


  The results obtained in this study indicate that the codon
  randomization method is a superior strategy for codon optimization. A
  significant improvement in protein expression was obtained for the
  largely established process of chymosin production, showing the power
  of this strategy to reduce production costs of industrial enzymes in
  microbial hosts. (Menzella 2011)


Stitching smaller synthesized fragments works well if you're pressed for time, but it's usually more expensive. However, sometimes these companies do special pricing on synthesis for &lt;1kb, which makes stitching a great choice. Turnaround is generally faster for three 1kb fragments than one 3kb fragment.