Livescope is a brand name of Garmin for Forward Facing Sonar. Lowrance and Hummingbird offer the same product/technology under different naming - Active Target for Lowrance and Mega Live for Hummingbird.
There is no "reasonable price" unfortunately. Well, there is one, but I will save that for the end.
First off, you have to have a compatible head unit/MFD. So unless you want to buy both the FFS setup and a new MFD (which leaves "reasonable" in the dust), you are limited to what electronics you are currently running on your boat now. Ie, if you are running Humminbird Helix but wanted to get Garmin Livescope, you would need both the Garmin Livescope setup as well as a Garmin head unit. So, if you match up to your current electronics, you will be far better off price wise.
Probably the best deal around right now is the Lowrance AT1 or a Garmin LVS32 setup. Lowrance just replaced AT1 with AT2, so everyone has AT1 on sale typically for a bit under 1K. Garmin replaced LVS32 with LVS34 so you can probably find similar deals on it as well. Hummingbird still only has the intial release of Mega Live, so you will likely be paying full price if you go that option.
Personally, I'm all Lowrance so have AT1. If I was starting over, I would proably go Garmin. AT1 is good, but Garmin's LVS34 is pretty much the top dog right now.
Also, just for info as a general comparison...
Garmin - first to market, considered the market leader at this time. Has best images, but requries the most work/tweaking of settings to get there.
Lowarnce - actually licensed in some way from Garmin I think - Good but not quite as good as Garmin. But, much simpler to setup, really only two settings to fiddle with.
HB - last of the three to the party. Has cleaner image, but worse target aquisition and seperation, as HB's focus was to create a cleaner screen than the Garmin. But in doing so they also miss some targets. Sort of like turning 2d filtering on, you clean up the image, but miss some fish in doing so.
Broad generalizations, really. All are good. HB has been getting better with software releases based on reports from ML users. HB also has target lock option, which sounds like it would be cool, but again adding much more complexity (and cost) so I won't add more to confuse
Honestly, pick the one that matches your current electronics... If you don't already have a MFD so thus would need to buy one also, I would suggest looking around for a nice Garmin LVS32/MFD combo deal during the memorial day sales...