Not sure who you're with now but a lot of parking companies are in the same boat.
There are a lot of reasons for PPC on a name. If the keyword is in a saturated market area (like computers), the domain is broad in meaning (not targeted or niche) then you may get a million views but a few clicks of low value. However if this domain name is specific or targeted to a niche, you might only get 5 views and 3 clicks at 30c PPC. Some small property related names I've got seem to do best, less views and clicks but higher RPM.
I've only parked less than 200 names, but it's the same accross the portfolio. Any names getting more views but less clicks = lower PPC.
Low click rates can be the main reason, no matter how many views you getting, the advertisers are paying peanuts for clicks because there are so many to go around. You are under their thumb. Look for good names targeting markets in high RPM areas.
I hate it when I add a name, see it getting more views than other names and then finding the click rate takes the wind out.. then I find advertisers from low RPM areas advertising on that feed - double whammy.
There's a good reason people pay good money for good names. Someone I look up to recently rammed that message home to me.. I'd agree at this point: why not spend the same amount to buy a few decent proven names for the year, rather than registering swathes of new untested names.
If your names are not making you happy at one parking company, you could try another out - but give a few months also. Some names only get a good mix of optimisation and search coverage after they've sat with the new parking page for a while - unless they're top notch type-in names, which should be the goal for your parking portfolio over the longer term.
Also consider developing names that are not returning investment on parking.
Typical me, long post, but hope it helps.. Anyone correct me if I'm wrong about the PPC etc - much appreciated.