I'm confused on transactions....can you help?

[t0nytk1]

Hello,

Today I transferred .15 BTC to purchase a T-shirt.   The vendor charges $19.99 or the equivalent in BTC which they stated on their site as .15. When I made the transaction (20 minutes ago) the price of a BTC was $132 which is the same as it is now.  The transaction went through and my blockchain application said it was successful but the USD value was $23 at the time of purchase? Huh?  I'm confused.  Did the price spike to above $150 for 3 seconds while it went through?  Kinda lost on that one. 

Also, last Saturday I purchased BTC via MoneyGram/Bitinstant....Minus the fee of $3.95 and the 4% that Bitinstant charges..my total amount of funds I sent was $135.  At the time then, the price per BTC was $123....so I assumed when the transfer went through I would receive 1.09 BTCs.  The transfer went through about 1 minute after payment and only 1.07 BTC was added.  Did the price jump to $126?  I checked and it was actually lower...around $122.

Neither example made me angry...just somewhat lost is all.  I'm assuming I'm missing something that is perfectly explainable.

Thanks for your input!

[t0nytk1]

Also,

When I purchased the tshirt.  I ended up scanning their QR Code with my phone and with my laptop clicked the payment had completed.  How the heck did the vendor know it was me that sent the .15 BTC?

[tmh222]

What exchange are you getting your prices from?  What exchange does your t-shirt vendor use?  and what exchange does BitInstant use?

[t0nytk1]

I get my prices from Mt. Gox which I believe Bitinstant uses.

That's all I know.

[t0nytk1]

but I guess I don't know who my app (blockchain) uses....or who the tshirt vendor uses.  With the tshirt purchase...everything went great...just confused by the application saying that the total USD value was $23 something.

[ranlo]

Prices can fluctuate even over a period of seconds. It sounds to me, though, like this is a situation of using different exchange rates. If you have questions I think the best person to ask would be whoever you sent the funds to. Explain what you know about it to them. They may be able to clarify things.

[DeathAndTaxes]

Also,

When I purchased the tshirt.  I ended up scanning their QR Code with my phone and with my laptop clicked the payment had completed.  How the heck did the vendor know it was me that sent the .15 BTC?

Most merchants use a unique single use address for each sale.  When you checked out the server assigned a unique payment address to your order.  When the right amount of funds were received in that address the server "knew" your order had been paid.

This may seem strange when thinking of other systems where the cost of producing an "account" is expensive.  A merchant wouldn't open 10,000 bank accounts and direct each customer to send payment to their unique payment account.  However the cost of producing a new address in Bitcoin is negligible.  A good system can generate a thousand a second easily.  We generate a new address for every order unpaid or not.

[DeathAndTaxes]

but I guess I don't know who my app (blockchain) uses....or who the tshirt vendor uses.  With the tshirt purchase...everything went great...just confused by the application saying that the total USD value was $23 something.

There is no central pricing authority.  The app could use just about anything for determining the exchange rate.  You should check with the app if it concerns you.  The exchange rate does fluctuate, there are multiple exchanges, the app could have been using delayed quotes, or taking an average to smooth out prices.  Lots of possibilities.  The only thing that is certain is the tshirt cost 0.15 BTC, you paid 0.15 BTC.

[t0nytk1]

but I guess I don't know who my app (blockchain) uses....or who the tshirt vendor uses.  With the tshirt purchase...everything went great...just confused by the application saying that the total USD value was $23 something.

There is no central pricing authority.  The app could use just about anything for determining the exchange rate.  You should check with the app if it concerns you.  The exchange rate does fluctuate, there are multiple exchanges, the app could have been using delayed quotes, or taking an average to smooth out prices.  Lots of possibilities.  The only thing that is certain is the tshirt cost 0.15 BTC, you paid 0.15 BTC.

Thanks! That makes sense and yes, at the end of the day I paid .15 BTC for what I wanted.

[t0nytk1]

but I guess I don't know who my app (blockchain) uses....or who the tshirt vendor uses.  With the tshirt purchase...everything went great...just confused by the application saying that the total USD value was $23 something.

I did some more checking and realized my wallet app was somehow tied to Singapore Dollars which also has the $ symbol.  I don't know how that happened.