I use a fish based fertiliser. In the UK, I get a Dutch product by Biobizz called Fish-Mix. Its currently about £24 ($27)/gal. I use it because all my plants like it! It's my main fert, applied roughly every 2 weeks, 5ml/L or 20ml/gal.
However, NPK is about 5-1-4, which they no longer publish. Product includes vinasse from sugar beet, apparently for feeding micro-organisms. I've read lots of info about how it's nitrogen/£ is poor value, and also that vinasse can deoxygenate soil etc, but I see better results from this than other fert.
My annual fert bill is £30, coupled with an alternate feed bill of about £40. Not bad for about 600 prebonsai.