In general, sprucing is what you should be doing, not replacing. Paint cabinets, replace knobs, maybe even a new faucet or sink can do wonders.
When selling a home the most important thing (in addition to pricing it properly!) is to make it as appealing as possible. Repair any broken items, clear up storage areas, declutter. Paint is the least expensive way to prepare a home for sale.
Don't spend too much getting ready - you most likely won't get it back.
RE/MAX Premier Properties
However in today's market what sells is Location, Price, Condition.
I just showed a home that is new on the market priced at 429K
It needs new Kitchen cabinets.
It has a new Refrigerator.
My clients see that it needs a whole new kitchen, They like the home, but want 30K for a new kitchen.
I think it is less expensive to remodel now.
The same rule applies when you purchase.
Good luck in your transactions
Are you a buyer trying to negotiate price? or a seller looking to give an allowance? If you are a seller and the kitchen/bath needs work, get some estimates like Kurt said. If you are a buyer, you can try to deduct not only for the actual cost of completing a renovation, but for the time/aggrivation you will go through while doing the renovating. As a buyer, though, the price of the house may have been determined taking into consideration the condition of the kitchen/bath as they are. Only your Realtor can advise you of that.
With the kitchen, can you paint the caibnets and change the hardware? You can also look at cabinet refacing. If you do decide to replace the cabinets, (and I would hesitate to do this), go with a lighter cabinet like maple. The standard builders oak cabinets looks cheap.
In a nutshell: I would replace the tub, spruce the kitchen up a bit & give a kitchen allowance. The actual amt of the allowance will very much depend on the price of the house. You can also get a quote for new kitchen cabinets from Home Depot or Lowe's.