The registration fee is £110 per LPA, but as MRs P only has her state pension she got a 50% reduction for each on.
We completed and registered both Financial and Property for each of us. (4 LPA's)
The online process was quite simple, you are guided through each section relevant to you (sections that become irrelevant due to your answers are not offered).
It costs nothing to prepare and print the LPA's. You can then check them (the longest part for us), get them signed in the order of the check list printed with the LPA's (you do not need any professional signatories, only people that have known you for a while)
Only once you have everything checked, signed etc and are ready to register do you have to pay, all of which can be done on line. It took about 9 weeks to get the registered LPA's back. You can register at any time, but IMO it is better done sooner than later.
During the preparation stage, if you decide it is too complicated (which I'm sure you won't} you can cancel everything and it will cost nothing, so well worth a try. The phone help line is also very good and friendly)
You get a year between starting the online application until you have to have all the signatures, so plenty of time, if, as in our case your attorneys do not live locally.
If I can help, PM me.