Yes, the price is different depending on where you start and end, and yes, I've used various countries for origination when the savings for the RTW ticket were noticeably greater than the cost to get to and from the start/end country. Over the years I've used Turkey, Japan, Sweden and South Africa in this manner. At the moment, Jordan and Israel are relatively "cheap" for business-class Oneworld Explorer tickets (also, surprisingly, Denmark) but not as cheap as some other places, namely South Africa and Namibia. But obviously getting to Jordan is (somewhat) cheaper than getting to, say, Cape Town, unless you happen to live in Hermanus.
One important factor, however, is that the base price for the RTW is only part of the story. Depending on who sells the ticket, and which airlines you take for various segments, fees and "fuel surcharges" can add up to 20% or more of the face cost of the ticket to the bottom line. In particular, British Airways really whacks you for fuel surcharges (shown as code "YQ" on the taxes and fees breakout) while tickets issued by American Airlines will have (usually) a much, much smaller number for "fuel fines." Stopovers in the UK will lead to having UK Air Passenger Duty assessed on your departure from the UK, which can also be a big number. There are lots of wrinkles in the price picture for Oneworld Explorer RTW tickets.
One last thing, I'd really urge you to think about business class instead of coach. The reason is that you can earn so many frequent flyer miles in a well-constructed business RTW that you can leverage extensive business- or first-class travel long after the RTW is finished. I personally buy a business-class RTW every other year, and earn enough miles (and FF status) that I really don't have to pay for a lot of travel in the "off" year. So if you think "strategically" you can stretch your budget effectively, and fly comfortably in the meantime.