At some point (a pair of distinct fee rates) the price for N bytes and M bytes can cost the same price.

Example: 

Tx_A is 1,000 bytes pays 1sat/byte
Tx_B is 500 bytes pays 2sat/byte

Both cost 1,000 sats

I suppose your example for 97/98 bytes would look similar.

Just because something is derivative doesn't make it not not real.

At some point the price for 97vbytes and for 98vbytes would cost the same price. Alas, this isn't a "problem" per se but what would that look like tho.

tomlaies

Transaction fee is quoted in natural numbers, e.g. 97 sats for a transaction. A fee-rate sat/vbyte is derivative and doesn't exist on the chain. There isn't any rounding problem.