As both an avid glider pilot and also airline pilot, I have never seen
one jet/glider from the point of view of the other, and I do look, if
I know the other is about. Transponders are essential if you want to
have any chance of seeing the other at high speed. TCAS is my main
alerter, especially in the US, where I am amazed that that VFR
aircraft have such freedoms in busy airspace, may they continue for
ever. A case in point, last night while on a night departure out of
SFO on climb to 3000ft, there was a Cessna at 3500ft directly in the
departure path doing what he had every right to be doing. According to
TCAS, we passed directly underneath him , thank you TCAS, ATC and on
behalf of the 315 sitting behind us.
Airlines, and especially Ryanair, will not finance any such fitment of
transponders in gliders, our salvation as glider pilots lies in the
low cost development of ADS-B. In the meantime, I'm off to organise my
bi-annual transponder and altimeter checks.

As I've said I think it is entirely reasonable to approach
carriers like Ryanair with suggestions for them offsetting your
transponder costs (or take the tricky step of taking that battle
public... does the flying public have a right to know this?). Glider
organizations really need to think through whether to take on this
issue or not, if not when there is eventually a fatal mid-air
collision they just won't have a publicly defensible position. In
areas of high density airline and fast jets and glider traffic, doing
nothing looks to me like a very poor choice.

I know from outside the USA it looks like the whole place is run by a
bunch of cowboys, but I hate to ruin it for you... there is no "just
screwing in" of transponder in the USA. A certified glider requires at
least an IA/A&P sign-off or maybe a 337 field approval, an
experimental one may be done by the pilot. But in either case requires
a RF signal and pressure altimeter check after install and ongoing
biannual RF signal tests. Approved transponder test stations are very
unlikely to just sign off an inspection if they have any concerns
about the transponder install. But.. yes things here are much better
than the silly regulations EASA loads on glider owners in Europe.

Darryl