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Webster 1913 Edition

Adj.

Inexpensive.

Milton.

Adj.

Not expensive; not costly.

unexpensive ‎(comparative more unexpensive, superlative most unexpensive)

(archaic) Not expensive; inexpensive.
- 1855, Journal of the Royal Horticultural Society (volume 9, page 205)
  An effectual and unexpensive mode of Protecting Wall-Trees from Spring-Frosts.