Running 3 #10's (stranded) in 1-1/2" PVC conduit. Total run 75 feet.
Does code allow me to have a splice within the conduit? Seems like it
is kind of accessible since I can easily pull it from both ends in
case of problems. Two 90° bends are involved but I am using long
sweeps.
BTW, while I'm typically not a cheapskate, on my retirement allowance
I would rather not pay for a new roll of wire ($65) when I'm only shy
a few feet. Buying a single 75' piece, by the foot, will still set me
back $30.

I wouldn't recommend a spliced connection in conduit. I don't believe code
allows it, but even if you made a successful soldered and insulated splice
that section of the wire would be "stiff" compared to the rest of the
flexible wire. It may make it more difficult to pull the wire through
conduit bends, and if the splice is not "mechanically" as strong as the
wire, you could pull the splice apart when pulling the cable. You would
never know if there is damage to the splice until you have an electrical
problem. For example, say a portion of the splice breaks but leaves a
strand or two of the stranded wire. It would work fine until put under
enough load to overheat the wire. This could melt the insulation on
adjoining cables and cause a short.

You didn't mention what this conduit run was for, but I suspect $30 for a
piece of wire is minimal compared to the rest of the project. Have you
compared the cost of the wire and conduit, against just running a bare UF
rated underground cable? If you're running conduit, you're probably
spending a little extra to do the job right and allow flexibility in the
future. Why cheap out on the last little piece of wire?

If you're REALLY strapped for cash, watch your local Craigslist for people
getting rid of electrical supplies, and/or post an ad that you're looking
for some. I sold a couple hundred feet of various cables a few months ago
for $10, and see contractors selling surplus all the time. There wouldn't
be any harm using a "larger" wire than you need (i.e. Using a #6 or #8
gauge wire in place of your #10), so that widens your options a bit.

If you're going to do the job, you might as well do it right...

Good Luck,

Anthony