When my Dad turned 60, we sent my parents on a long weekend trip to NYC. We bought them tickets to a broadway show and gave them some spending money. Since Mom and Dad's birthdays are 10-days apart and they were married on Mom's birthday, we gave them this big gift as a combo-deal.
BUT, there are 4 adult children and their families that chipped in on this, so it maybe cost $200 or so per family.
For Mom's 60th, we chipped in again (combo-deal) and bought them a killer gas grill for their deck that has a rotisserie built into it, with rear burner and a deep fryer. Again, about $200 per family.
For their 40th wedding anniversary, again, combo gift, we took them out to a surprise dinner. They only knew that 2 of my sisters would be there but everyone came in from out of town to celebrate. At the dinner, we gave them a Western Caribbean cruise with air and pre-flight hotel paid. We gave them money for their taxi r/t to the port and money for gas and tolls to get them to the Newark airport. I can't remember exactly what we all paid for the trip, maybe $300-350 per family.
They have been thrilled with all of these gifts.
I don't know what you can afford, or where you live, but a night away somewhere might be nice if a weekend costs too much.
Next big gift we're considering is hardwood for at least their dining room. Dad's opposed to it because he remembers what a pain they were to keep in our old house, pre-polyeurothane days. Mom would love them, though, and Dad would give in to what Mom wants.