I never discovered a truly cheap speaker that really worked for me, but Spica TC50 or 60, ADS L400, L500, Harbeth HL are quite good, if not cheap in their day. Dahlquist M903, 905, 907, etc. are worth a listen. Any of these can be real bargains, depending on operating condition.
Some classics were quite good, such as L166, L96, L220, 300s, ADS L1090-1590 (especially 1590!) are great to hear, but often not cheap enough to compete favorably with better designs of today.