Affordable LRGB filters, suggestions?

What scope are you using? does it need careful backspacing considerations or has a coma corrector/field flattener? If so, make sure you purchase filters which are the same glass thickness as your SHO filters - this is because you will need to account for (1/3rd) the filter thickness when shimming your backspacing. 

FWIW I personally have Baader LRGB and SHO filters and have zero complaints.

Filter thickness will matter for focus offset if you ever choose to use that feature. I have and use the ZWO 2nd gen LRGB filters ($199 at Agena Astro for 36mm). Very inexpensive and they work fine with my triplet scope but for my doublet they go to far into the blue spectrum. I am currently saving for a set of Astronomik for my doublet scope.

Few issues to consider. filters tickness are 1mm (Astronomik), 3mm (Chroma (I think) and Astrodon), and 2mm (Baader, Antlia, Optlong, ZWO). 
Different Filter thickness can produce problems with backfocus (in particular for fast optics) and when you use an OAG. But since Chroma and Astrodon are not really discount, and also Astronomik is similar if not more expensive than Antlia, this is probably not a problem you are going to have. If you stick with one of the 2mm brands, you probably will be fine (I, e.g. mix optolong NB with antlia LRGB, and the focus point is (almost) identical. almost = well within the CFZ).

The other issue you want to consider is the transmission curve. Optolong, Baader and ZWO open up in B quite early, at around 380nm - which is nice (you get more light) for a reflector. But for refracting optics, trouble increases the bluer you go, so having a 420nm cut off like Antlia or Astronomik may be beneficial. For R, the Antlia open relatively late - which has pros and cons. con: you are losing light, pro you cut the more light polluted spectral range (in particular in areas that still use sodium lights).

personal opinion: since you have a refractor, you probably go best with the Antlias. YMMV.

Matthias