That's a good deal!
They do seem chaper than one of my suppliers for things like LEDs and semiconductors but they don't stock a great range and they are more expensive for speakers and piezo buzzers.
A small speaker: $1.55 at Core, $0.99 at Rapid
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A piezo buzzer: $4.07 at Core, $2.77 at Rapid
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Exchange rate, at the time of posting: £1.979/$.
The moral of the story is, just because one or two products are very cheap from one supplier, it doesn't mean they're cheapre than another supplier.
Also I don't know whether it's worth paying for shipping - it's probably only worth it for large orders or items which are very cheap at Core compared to local suppliers.