In a situation where one has that much money to blow on something so limited, virtually anything would've sufficed.
We did a trivial test of Splunk at my last company, it's extremely expensive and it's very easy to bump into its limitations. We were able to wreck the poor Splunk server with some rather sundry queries into a dataset that shouldn't have been that big of a deal. Issues that we took back to the company and didn't get any real answer on.
Its popularity leads me to surmise that there is still a lot of money to be made in solving mundane problems. (Which is good news if you're a product-minded programmer)
What is extremely expensive for you? We find the overheads on storing & processing the data are much more than the cost of the license, on a per GB basis.
Without knowing details of exactly what you are doing it's difficult to comment on your problems with queries. It's true that something like Solr gives you more control over the indexing process, so you can optimize it more for specific queries. Splunk tends to rely more on saved searches (and the new search acceleration feature).
We have a couple of datacenters, so yes, we have more than a couple of servers.