Is it worth 200 dollars to resize a size 4.5 18k white gold bridal set with 0.45ct tdw diamond to a size 7 The ring cost 250 used?

Answer 1

Your answer depends on your intended use of the larger ring. If a $200 investment will satisfy your intention, then, yes, the investment is worthwhile.

The expense is probably mostly the current high price of gold, and the craftsmanship involved with up-sizing the ring.