Calculation via drop-downs - possible, or alternative option?

Hi there,
As I type this I'm not sure this is going to be possible - or at least the right way to go about this.
I'm rebuilding an existing form, which has a number of fields (with prices) as drop-downs.
This will give you an idea;
https://www.evernote.com/shard/s3/sh/ff900ba9-e292-4b3a-8768-180cdfa31a3f/04a6a65320f2490898a396cda9155dd0
The first drop-down has 3x other options - all with different prices.
The second drop-down goes all the way up to 10 nights - so that's a lot of possible combinations.
The second drop-down only appears once the user has selected an option from the first.
There is one more field using the 2x drop-down scenario.
5x others that only make use of the one drop-down (with prices).
The end scenario is that all these get added up (somehow?!) & the user then gets directed to PayPal to purchase whatever options they have selected.
Phew.
Somewhat complex (for me at least) so any advice would be very much appreciated!
Thanks,
Jas

Thanks Chris, I've started playing around with the various Pricing Fields too - this may well work ok, so I'm open to options - whatever you think best.
Cheers,
Jas