Apple's operating systems used to be $129 for each release. Now they are only $29.99 for 10.6 and $19.95 for 10.8. Be glad they didn't ask you to pay for both 10.6 and 10.7 to get 10.8.
Furthermore 10.6 gives you the opportunity to see if you still require Rosetta, the application that supports PowerPC applications side by side with Intel Mac applications on an Intel Mac. Neither 10.7 nor 10.8 give you that opportunity, and downgrading is not easy. So backup your data, regardless of which path you choose, and recognize the compatibility limitations of each operating system: