Definition of costful in English:
costful
adjective
1Expensive; sumptuous. Now rare.
2Involving or characterized by expenditure or loss (of time, effort, etc.); costly. Now somewhat archaic.
Origin
Middle English; earliest use found in Ayenbite of Inwyt. From cost + -ful.
Pronunciation
costful
/ˈkɔːs(t)f(ʊ)l//ˈkɒs(t)f(ʊ)l/