EURUSD: obsessing over tenths of a pip vs reading structure

[FXS London Scalper]

There's a type of scalper who will switch brokers to save 0.1 pip of spread, then take a trade in the middle of a range with no level behind it. The cost saving is real, but it's small next to the quality of the entry.

Rough math: at 20 trades a week, 0.1 pip saved per trade is 2 pips a week. One poorly placed entry with a 5-pip stop costs more than that.

That doesn't mean costs don't matter. They matter a lot for scalpers. It means there's an order of priority:

1. Is there a reason to be in this trade at this level?
2. Is the expected move big enough relative to cost?
3. Then, can the cost be lowered?

Signs the balance has tipped too far toward costs:

- More time spent comparing broker spreads than reviewing trades.
- Taking more trades because each one is "cheap".
- Rejecting a good setup on GBPUSD because EURUSD is 0.3 pips cheaper.

Signs it's tipped too far the other way: never having calculated what you pay per month in spread plus commission.

Where do you draw the line between cost discipline and over-optimisation?