Auction price databases

There are multiple auction price data providers on the market. These providers offer access to their price databases at very different prices and comparing the different subscriptions is not easy as the pricing is sometimes not very transparent.

Hence the question arises: Do you actually get more for paying more? I compiled the following table so that collectors, art lovers, appraisers, auctioneers, researchers and everybody else that wants to know how much a work of art is worth, can find the provider that suits their need the best. Many of the providers offer extensive features that others don't.
I hence focused this comparison table on the following core features:

1. The Size and scope of the realised auction price database
2. Features: Can upcoming auctions be searched as well? Is there an E-Mail Alert for upcoming auctions? Is there an artist directory? Are additional decision support tools offered (analysis tools, summery statistics etc.)?
3. What core features can be accessed for free?
4. What is the price for the cheapest subscription offered? (note: if the cheapest subscription does not offer free access to the database I tried to add the price of the subscription that does)
5. What kind of features are included in the cheapest subscription offer?

I ranked the companies on a scale from 1 to 3 (1 being the best) for all categories and added an average rank in the end. All data was collected on the same day. I hope the data is correct. Please double check before subscribing to one of these providers. Sometimes there are special offers. If there are updates or other providers, please comment and I will try to edit the table as soon as possible. If you have ideas for more Categories to Rank please let me know!