Forbidden Melding Rates

[Squa]

can't you meld low quailty materia to open up the spot, then overmeld with expensive materia after?

[Feilina]

OP, it could have been worse. In 1.2x you had lost your item, your materia, your carbonized matter and all materia already slotted.
Take it this way and you are a lucky guy.

You tried playing lotterie and lost. Take it like a grown.

[Raminax]

can't you meld low quailty materia to open up the spot, then overmeld with expensive materia after?

Quite the contrary, actually. If money is an issue, you want to meld the highest grade Materia as early as possible in the (over)melding process, because they have the highest chance to fail and blow up.