Money is power, so long as people agree upon the value of your wealth.
You, the DM, shouldn’t have to be turning cartwheels to help players figure out how to spend their money. Players should run their characters asking that very question: “Now that I seem to be rather well-off after some rather lucrative adventuring, what do I do with it all?”
What to do with one’s wealth is as valid a question in a medieval world as it is ttoday. And a really good roleplaying theme, if you ask me. Lots of juicy moral and ethical dilemmas in there (potentially), and that aside, lots of possibilities.
Wealth gives options. Didn’t you always want a nice house to live in? Heck, maybe a small manor and manse in the country? Ah, but surely others will hear of the wealthy adventurers moving out here, and surely they must stash all their loot there…
Make sure you know where your PC’s stash their loot. People with lots of money have big targets on their heads, especially “new money.”
In general, great wealth means a chance to affect society. While you don’t have to play BR on a domain level, I wonder how you can entirely ignore the domain level when it’s sitting right there, just asking to be involved…
Higher-level PC’s with lots of money are unavoidably going to become people of power and consequence. The more their fame and wealth grow, the more their actions will ripple through the fabric of society and have broader consequences - whether they wish it or not. Good-aligned characters should then feel a degree of responsibility to be careful with that wealth and power. Evil ones might see the opportunity to start building their own little kingdom, or trade empire, or just have a really paranoid, trap-ridden hideout for their goods. ( You want 'em to blow money, just have them start detailing the cost of a few sophisticated traps and structures to protect their treasure! 
Also: don’t forget nobles looking for loans (at interest, probably) or traders/ merchants looking for investors. Might be interesting to have the characters get talked into throwing their money into a risky but potentially ‘big gain’ speculative venture. And if the goods don’t get there (or back), the PC’s might have an adventure tracking down where their money went. Which could mean a crooked merchant who took the money and ran, an earnest trader who fell afoul of a hostile reception or was waylaid…what if it was the return voyage, laden with a wealth of foreign cargo, was pirated or redirected (perhaps by a mind-influencing villain???).
‘What to do with the money’ has a wealth of story potential.
Osprey