Lapua .308 cases aren't cheap, but anything will be cheaper than new 7mm-08 cases. This will work on any cheaper brand of new .308 cases as these are undersized to begin with. In fact you're only partially sizing the neck here with minimal body contact usually, so may not need lube at all.
The 7mm-08 case is 20 thou longer than .308 Max length so any converted cases should be OK for length. Necking down .308 gives more uniform results than opening up the necks of .243 cases but part of the neck remains oversize, which might cause tight chambering in some rifles. Bk has a point about over thick necks needing turning, but I would think that most sporting 7mm-08 chambers should have enough lateral clearance to take marginally reformed brass like this.