I think diy acrylic is only cost effective when you want to maxime the space inside the cabinet under the display tank and you have a unique partition setup for your refugium/filtration needs.
but imo for any thing 29G or less I would buy a 10G tank $10 a 2 gallon bucket with lid$5
plastic dollar store pot scrubbers $3-5. glass sheet from HD or glass shop for partitions $3-$12 (depends on the # of glass partitions), PLastic cealing light bulb fixture $1.25, dollar store 6foot extention(for the sump light) $1. a cfl screw bulb 13watt $9 for 4pk @ hd. a 350GPH pump $20-35 and bulkheads you can get cheap from these ebay sellers based in texas (forgot thier name) HD for 1" and 1/2" plumbing
any who even with all the $ in the aforementioned parts its still cheaper than the cell cast acrylic alone and then you still need to order all the other stuff