costly

As an adjective costly

is of high cost; expensive.

As a noun null is

zero, nil; the cardinal number before einn.

As a letter s

is the letter s with a.

As an adjective costly is

of high cost; expensive.

As adjectives the difference between pyrrhic and costly

is that pyrrhic is (label) of or relating to (319/318–272 bc), greek general and statesman while costly is of high cost; expensive.

As adjectives the difference between psyched and costly

is that psyched is thrilled while costly is of high cost; expensive.

As adjectives the difference between costly and overpriced

is that costly is of high cost; expensive while overpriced is priced higher than what it is really worth.

As a verb overpriced is

(overprice).

As a noun premium

is bonus (extra amount of money given as a premium).

As an adjective costly is

of high cost; expensive.

Wealthy is a related term of costly.

As adjectives the difference between wealthy and costly

is that wealthy is possessing financial wealth; rich while costly is of high cost; expensive.

As a noun wealthy

is (uncountable|preceded by the)   rich people.

Costly is a related term of sumptuous.

As adjectives the difference between costly and sumptuous

is that costly is of high cost; expensive while sumptuous is magnificent, luxurious, splendid.

Costly is a related term of generous.

As adjectives the difference between costly and generous

is that costly is of high cost; expensive while generous is (obsolete) of noble birth.

Costly is a related term of lavish.

As adjectives the difference between costly and lavish

is that costly is of high cost; expensive while lavish is expending or bestowing profusely; profuse; prodigal.

As a verb lavish is

to expend or bestow with profusion; to use with prodigality; to squander; as, to lavish money or praise.