With so many different devices and operating systems it is frustrating to determine the variables.
One a side note i see that Michael's picture of his Jeep, he states is 3.34 MB. To me that is a BIG file.
I reduce all of my posting greatly from their original size, generally 5 megapixel, to much smaller, reducing them on average to about 25% of their size. I base this percentage on if i will be doing any cropping.
I posted 9 Redline Darter photos on my recent Little River account and all 9 images only totaled 1.07 MB. I ain't no master photog like many others but even then when sharing images on the NANFA forum massive files just take up lots of unnecessary digital space, which NANFA pays for. Thus i reduce near all my photos for posting.
Another example is the Star photo leading into the series of July 3 postings. The photo's original size is 2.15 MB. After reduction it became 101KB which is a fraction in digital size, yet appears the same visually for this usage.