Why spreads differ from broker to broker - confused

hi guys,
my question is why spreads are differ from each brokers and somebroker it is too low, someother it is too high, or my thinking is wrong ??

eg:
1 lot gpbjpy
fxcm - 7 spreads + $8/lot commision
oanda - 26 spreads + $0/lot commision

so in 1 lot, 1 pip = $10,
fxcm = 7 spreads + $8/lot commision = 70+8 = $78
oanda = 26 spreads + $0/lot commision = $260 + 0 = $260

is it correct calculation ?
why fxcm is low and oanda is too high ?
which broker to choose ?
is there any advantage to choose high price of oanda ?

1st they are different model brokers.
Fxcm is a marketmaker and a ecn broker.The commision model on fxcm is on the ecn model
Oanda is a market maker.

2nd, your calculation is wrong.
The current pip value for 1 lot (100,000) of GBP/JPY is $8.89537

Fxcm spread 0.7*8.89537= $6.226759 + $8 = $14.226759 /lot
Oanda 2.6 * 8.89537 =$23.127962

Conclusion: with fxcm you get lower spreads and lower commission
Choose a broker that is regulated (uk) preferred
If you're outside the USA I don't see any reason to choose oanda...

Why are goods cheaper in some shops than in others?

I spreadbet GBP/JPY with a spread of 2.5 pips. You should not use a broker that offers a wider spread than that.

any cheaper alternative broker for gbpjpy ?

For a spreadbetting account, not that I know of.

Tickmill has 1.5 pip to 1.6 pip spread for gbpjpy + small amount of commission.
I use them for eurusd: 0.1 pip to 0.2 pip (that's the fifth figure behind the decimal !) + 2USD per 100.000 USD traded

its my calculation correct ?

FXCM :
Eur/usd (1 - 2 spread + $8 commision :
1 spread + $8 = 0.1 + 0.8 = 0.9 pips to reach No Profit/No Loss line
2 spread + $8 = 0.2 + 0.8 = 1 pips to reach No Profit/No Loss line
Rebate : 17 % if deposit $150k or more / or 500 lot per month trade volume to claim rebate even after trade.

Tickmill :
Eur/usd (1 - 2 spread + $4 commision/$3.2 commision :
Pro account :
1 spread + $4 = 0.1 + 0.4 = 0.5 pips to reach No Profit/No Loss line (0.3 pip after rebate)
2 spread + $4 = 0.2 + 0.4 = 0.6 pips to reach No Profit/No Loss line (0.4 pip after rebate)

Vip account (need 50k Deposit) :
1 spread + $3.2 = 0.1 + 0.32 = 0.42 pips to reach No Profit/No Loss line (0.22 pip after rebate)
2 spread + $3.2 = 0.2 + 0.32 = 0.52 pips to reach No Profit/No Loss line (0.32 pip after rebate)
Rebate : Fixed $2/lot for Pro and vip


Offtopic:
As i am newbie, first i want to reduce losses (this commision thing reduce loss a little or take little more time to blow my account) or reduce the extra capital for new account.