i think to control the economy you could do it like this for example
to repair 1 star items
white - 200 silver
blue - 400 silver
purple - 600 silver
2 stars item
white - 300
blue - 500
purple - 700
’
’
’
6 stars item
white - 1000
blue - 1700
purple - 2500
and so on
this way the player can pay for the repairs and you can control the economy