I work in the insurance industry and have investigated this issue recently with a number of general insurers.
Firstly the terms and conditions from insurer to insurer vary significantly. One thing one insurer may accept another will not. The one thing that is in common is keep photographic and written record of everything that you own and have bought. If you cant prove you owned it you will struggle to get paid. If you cant prove what you paid for it you may get screwed.
Secondly - be very careful being insured for "specified items". The guy on the phone selling this to you gets paid a commission on the sale - the higher the premium the higher the commission. However they are not the ones paying out claims. I have worked for one of the big 4 banks (that is also one of the top general insurers in the country) and i can promise you that 90% of the people selling this cover are only interested in getting a sale and they are taught to up sell on the specified items. Make sure you read the terms and conditions carefully - dont believe a word someone tells you one the phone. In the event of a claim "the guy on the phone told me this" does not mean jack.
Thirdly - the problem you have with cards are that unlike items like jewelery and musical instruments they are not as easy to value for the insurer. I have spoken to a couple claims managers and asked how they would value these items and basically they have told me the insurer has a couple "expert" antique/collector dealers on the books that values this type of stuff for them if you cant produce receipts for what you paid.
My advice is to speak to an insurance broker as most should be able to give you better advice than just speaking to an individual insurer. Make sure you are very specific on what you expect from the cover. Its not about how much the premium is its about what your going to get at the time of a claim.
My collection is insured through NRMA. I basically estimated what it would be worth to replace if I lost everything and asked them to insure it for that amount. Their only concern was proof of ownership and I mentioned to them that I have the entire collection catalogued on my website, which they accepted.
Might be a different story if it came down to making a claim, but I sleep better at night knowing I have some coverage for my hard earned memorabilia.
Just to give you an indicative price, I have insured my collection for $40,000 and pay a premium of $86.76 per annum on this component. I'm sure NRMA are not the cheapest option around, but I have had good experience with them when making insurance claims in the past, so I decided to stick with them.
I recommend that at the very least everyone should record their collection and the price paid for each item on a spreadsheet or database and keep a copy offsite.
Just to add. I heard about a local stamp dealer who passed away a few years back. He didn't have current pricing on any of his merchandise, as he knew what his items were worth. However, when he died, his family had no idea what the value of his stock was and it's a well known fact in the circles that some of his fellow stamp dealers took advantage of this situation and bought his stock for a fraction of their true worth. So definitely worth recording prices, regardless of whether or not you have insurance on them.
Just check the fine print guys. You need to know if your insured for an agreed value, market value or purchase cost and what your going to have to provide to substantiate this at time of claim.
I just went by beckett value, then converted to aussie dollars. Back when I originally insured my collection, the dollar was weaker, so my garnett collection was close to $5k with just 275 cards. Now that the dollar is stronger and I've got more cards .... I'm going to have revalue my collection. Goodthing I know the basics of database.