Saxo brokerage charges 0.5% markup on the spot FX if you trade US stocks on a SG funded account. Is this a standard FX markup across other Brokers?

I just want to add here that the markup is now 0.75% for the standard tier of accounts! For a user of Saxo I was quite miffed that this wasn't made clear to me. I only realized it when i examined my trade details closely and saw the figure "USDSGD+-0.75". Then I thought to myself, "I could've sworn it was 0.5%" before.

Then i examined reports that I exported from the platform, looking at trades in mid 2019 and now (Jan 2020), and found that the rates are indeed increased.

Depends a bit what you are comparing against,

For payment services (credit cards) - 0.5% is very competitive compared to fees that banks hit you with (ranges from 3-4%)

For pure FX brokers - 0.5% still competitive but attainable for various sources but the advantage, in this case, is that you have it integrated with your share trading facility.