I have LR4 what to upgrade to 6 how much does it cost? also will i loose any of my preset i have already in lr4
In the US a LR upgrade from one serial-number-licensed version to another is $80.
A LR CC (plus Photoshop CC) subscription costs $120/year payable in $10/month for the full amount.
Generally presets will continue to work, although there may need to be some manual copying of preset files from the old LR place to the new LR place if you have them stored in a non-standard-location, now.
If you’re not sure what you want to do, yet, download the LR CC (and Photoshop) trial, which gives you 30 days to decide. If you go with a LR 6 serial-number-licensed version then you’ll lose Dehaze until LR 7 is released many months from now.