booking via vs amex card

I am thinking of taking the extended family on a trip to Cancun with Virgin Hols. Total cost approx 10K. If I book using my Virgin AMEX card there will be a cost of £260 however at 2 miles for every £1 spent I will be credited 20,000 miles. I think this is good value but am I missing some obvious problem with my thought process?

[Neil]

No, pretty it's pretty much as you said, do remember if you are booking online, make sure you go through Quidco or the VS shops away site for cash back or extra miles. This obviously doesn't work if booking over the phone.

edit: Just seen Mexico is excluded from the 2.5% cash back on Quidco for some reason!

VS sell miles for 1.5p each so by that token 20,000 are worth £300.

So you could look at it as you're getting £300 worth of miles for a £260 fee - a small win.

It all depends how much you need the miles though. If you don't really need them, you'd be £260 better off paying by debit card.

I'd do it on a black amex card if I had one, but the 2 for 1 on flights on the white card is barely worth it after the fee.

thanks guys