Nintendo has said that 3DS games will be priced the same as DS games, so we can expect most of them to cost no more than $30-$40 dollars.
Also, yeah, PS1 discs generally take up well under a gigabyte of memory. By way of comparison, Final Fantasy VIII, originally a four-disc game on the PS1, takes up less than two gigabytes of space in its emulated version on PlayStation Network. So yeah, it should go without saying that the 3DS cartridge size is big enough to handle PS1 games, even multi-disc ones.
That said, I think a lot of people on this thread are kinda jumping the gun. Perhaps I should reiterate: THERE HAS BEEN NO STATEMENT OR ACTION FROM SQUARE ENIX TO EVEN REMOTELY SUGGEST THAT CHRONO CROSS, OR ANY OTHER PS1 GAME FOR THAT MATTER, IS BEING REMADE FOR 3DS. Definitely do pester them about it, but let's not get excited yet until we have something to get excited about.