From what I've read the avg tx fee for BTC is $8+ per transaction (is this correct?)
Seems unlikely.
This site:
https://bitcoinfees.21.co/suggests that the typical fee right now is about 0.00000300 BTC per byte.
The typical bitcoin transaction is approximately 372 bytes.
0.00000300 BTC per byte X 372 bytes = 0.00111600 BTC
At the current exchange rate of approximately $4975 per BTC...
0.00111600 BTC X $4975 = $5.55
and the avg transaction fee for Bitcoin Cash BCH is 0.3 USD .30 cents (is thao correct?)
I don't know. I don't pay much attention to what's happening with BCH.
if so why and how could there be such a difference?
More people want to use Bitcoin, so they are willing to pay more for the limited space available.
I know more miners =lower fees but that much lower?
Not true.
more transactions = higher fees. Less transactions = lower fees.
The number of miners doesn't directly effect the transaction cost.
The relationship is mostly the other way around...
If there are more fees (and therefore more money to earn from fees) then it will attract more miners.
Make sure to read this over and over again. Nowhere in any calculation will you ever see how many dollars it cost to send bitcoins so you need to get the terminology down pat to understand where the fees are coming from.
All in all, bitcoins are more popular than that 97% mined by bitmain altcoin known as BCH. That's why the fees are higher. There are more transactions, so the blocks are more full so you need to pay more than the other guy for yours to go through first. BCH has cheap fees because it's a shitcoin that no one uses now, nor will they ever.