Sure, just relicense your application under the GPL. You're getting these libraries for free. If you're not at all willing to contribute back, then you're obviously not the target audience.

If you check Gtk+'s history, I have contributed back on numerous occasions.

Unfortunately, convincing the people who write my paychecks, VMware, to contribute Workstation and Player to the Open Source community seems to be a pretty big stretch.

"(1) If you statically link against an LGPL'd library, you must also provide your application in an object (not necessarily source) format, so that a user has the opportunity to modify the library and relink the application." - http://www.gnu.org/licenses/gpl-faq.html#LGPLStaticVsDynamic

So there you have it. Link statically against the LGPL library and package the object files of your commercial application.