Hi MMM,
there certainly is quite a difference in the prices of the players you are looking at! Depending on trades left, cash generating options, and what your relative opinion of the players involved scoring potential is, you might need to shop smart, over shopping to your wishes.
If we were to ignore the above, I'd say you got here without Ruck cover, go Zorko over Lycett. Depending on who you have sitting at F7, who your Rucks are, and how often you think you might need the cover, Lycett could be the smarter choice. If you think your F7 is worth 65 points, and you'll need the cover twice, then Zorko (assuming he and Lycett play all the remaining games) needs to outscore Lycett by around 16/game to be a better pick. I actually think Lycett can give us something around 95-100 with NicNat out, leaving Zorko to get 111-116 to be a better pick, IF ruck cover is required twice. A tall order, as I believe Zorko might be more 100-105.
There are so many things you need to factor in here, before making your decision. In general, I wouldn't be paying $60,000 extra to get 5/game, if you have other areas that need attention as well. If you think the $60,000 will get you 10/game, then you start to get into an area, where you'd say "Hang it, I will pay the difference!".
Really tough decision, and I probably haven't helped much (sorry), but it's a bit hard to know, without having all the information at hand.
Good luck, I hope you jump the right way.