I'm still not really sure why people are so worried. Logically, the sequence of events
@Browniee posted a while back is the only one that makes sense. So there are a few potential outcomes, bearing in mind Bilbao don't want to sell to us:
1. We complete the signing at the buyout figure without paying any extra in taxes
2. We complete the signing at the buyout figure and pay the additional taxes
3. We pull out of the deal for the only reason left at this stage: the increased price due to taxes.
4. If, as in 3, taxes become too onerous, we chuck Bilbao some more money to keep them happy.
1 is what we all want at this stage. 2 is only an issue if the club is being forced to pay the extra because they didn't know that they'd end up paying the taxes and are now boxed into a corner by how far along the 'deal' is. 3 likewise, if we think the player isn't worth an increased fee, we shouldn't pay it. 4 isn't likely as Bilbao probably still won't sell.
So it seems to me that the club can only really be criticised if they didn't know they'd have to pay the taxes, or didn't have the right advice/information about the avoidance of tax on buy out clauses. Because Bilbao refusing to sell, if the law/Spanish Revenue states that we have to pay tax on the fee, then we were always going to have to pay it if we wanted to sign him, regardless of whether we'd all had our hopes built up. So the decision would have been purely about whether the additional taxes on the already high fee were worth it. If the club thinks so, what difference does it make to us?