There is not really a typical write latency. It depends on the card design, its history of use, how it was formatted, how fast you are trying to write in blocks/second.
I wrote a test program, SdFatRawWrite. It is included with SdFat in the extra/examplesV1/SdFatRawWrite folder. SdFat has had raw write for a long time.
I like SanDisk cards, 1 GB or 2 GB formatted FAT16.
I ran SdFatRawWrite on an old 1 GB Sandisk Ultra II card formatted FAT16. I wrote a 10 MB file at 102,400 bytes per second. The result was:
Start raw write of 10240000 bytes at
102400 bytes per second
Please wait 100 seconds
Done
Overruns: 0
Elapsed time: 100000 millis
Max write time: 828 micros
This card has extremely good performance. The max time to write a 512 byte block was 828 usec.
This card was manufactured in 12/2006. Many newer cards can't beat it.