I was attempting to create a magic item and the numbers seemed a bt ridiculus, so I priced out the example on the table, which should be a clear example, and it didn't add up.
For a use activated item the example is the Lantern of Revealing which has a cost to create of 15,000. Invisibility purge is a 3rd level spell by a level 5 caster, it has a 1 min/lv duration and does not use a body slot. So 3x5x2000x2x2=120,000 which is eight times the listed price.
I was attempting to create a bag/other item, into which you could place a Bag of Holing or Portable Hole and take it into another BoH or PH without the dimension rift, you would not be able to safely access the BoH/PH while it is in the other BoH/PH (the 'Bag of Safety' must remained sealed in the extra dimensional space). Dimesional Anchor(4)(1 min/lv) should be an adequate spell to do the job. 4x7x2000x2x2=224000 seemed a bit too high a price, esecially since a BoH IV costs 5000 to make and is a higher level spell.
Generally, non-equipped items don't apply the "does not take up a body slot" cost increase, as long as you have to hold it to gain its effect or otherwise activate it in some way. That would halve the cost on both of your items.
With that said, you still run into the problem that magic item prices make no bloody sense whatsoever. D&D 3.5 is terrible about this, and it is one of the things that Pathfinder made no attempt to fix whatsoever, probably on the basis that it was too complicated.
That leaves you with two options. First, you could make up prices by just comparing your new items to existing items on an ad-hoc basis. That's what Pathfinder already does, so you're in good company. Second, you could build a new magic item pricing system. However, you won't be able to build a system that gives you the original prices that items have (because they are assigned more or less arbitrarily). Thus, even if you can build such a system, it won't make much sense unless you convert the existing items to your new pricing structure. And that's a huge change.
So you should probably just make up the prices and go with something that seems reasonable. Unless you want to rewrite all the magic item prices - in which case, we should talk, because I have a system that does (mostly) does that. :)
You could just reduce the cost on the basis of "It doesn't hurt anyone". On the other hand, just take the rule that "putting a bag of holding in a portable hole tosses everyone into the astral plane" and run over it with your GM Fiat till it's destroyed. So many better rules were dumped and that kill the party nonsense was kept on.
Note that these are all prices, not costs. A bag of holding IV has a price of 10,000 gp. A lantern of revealing has a price of 30,000 gp. An item that casts a 2nd level spell once per day would usually have a price around 2,400 gp. You calculate the price first, then divide that by 2 to get the cost.
For the second example, there's no reason to use the duration multiplier. In this case, you're not using the spell because you're attempting to cast it and make it continuous. You're just using it as a thematically appropriate requirement and something to base the price on.
The way I estimate prices for random items like this is to figure out what level the effect they're creating would be as a separate spell and work from there. I usually do this by taking the closest existing spell thematically and bumping it up or down a level. For your bag, it's nowhere near as versatile or powerful as a full blown casting of dimensional anchor, so I'd lower the level (or find a different spell). That'd bring the price down to 30,000 gp. Now, whether or not you'd pay 3x to make a bag of holding safe inside a portable hole, I don't really know.
As for the lantern, I'm not sure why they left off the duration multiplier since it would seem to apply here, but otherwise it matches the price given by the formula. (No lantern uses the slotless multiplier.)